Sounds pretty rough! I would say this is definitely a variety of issues all happening at once, most of which are your partner's responsibility to address. First and foremost, if the girls' mother bad-mouths you or their father, the kids are going to feel they can do. It's disrespectful on her end and of course if you were doing the same about her, she would have an issue with it! Your partner needs to address this either through a mediator or a lawyer if he hasn't done so already, not to mention that accusing you of trying to drown and poison the youngest girl is very serious and could cause your partner to lose his rights to visitation. I would speak with a lawyer about it because you don't want these false accusations popping up at some later time. Next issue is the younger girl's lies. Now, maybe she really believes you are mean to her, whether through a child's misinterpretation or because of her mother's influence. Either way, your partner and you should sit down with her and discuss the situation. Sometimes children feel guilty for liking their parent's new gf/bf, but in your case you have been together for a long time. She may just be feeling this guilt or there could be a number of other things happening that are causing her to feel the need to stay close to mom and stay away from you. Talk to your partner, he needs to talk to his ex and you both should talk to the kids. I hope this helps, I know it can be so frustrating and exhausting. Best of luck!

Let your SO parent his own kid. You can't be blamed the 'bad guy' if it's him doing the parenting. If she's not doing her chores and homework, let Dad get on her.

You get looked at as the 'mean lady' that expects her to do chores and figure out homework AND Mom is having parties and fun events over at her house....eh, at age 10 if somebody was going to give me a choice I'd pick the parties and fun too.

Your So needs to start dealing with his daughter and following through with his expectations. He needs to stop letting a ten year old call the shots on whether or not she wants to come over or gets to leave early. Who's the parent here? It doesn't appear to be Dad.

If you are going to have the slightest possibility of being excused of abusing the child (poison and drowning??) be sure you are never left alone with the child. What's happening with the BM telling the girls bad things about you and their father and bad mouthing is PAS. Google it and read about how parents deliberately try and alienate the children from the opposite parent. the more you realize and understand what is happening, the better your SO will be able to deal with it. But first he's got to motivate himself to parent his child instead of placing you in the line of fire.

'be sure you are never left alone with the child.'

& even that won't guarantee that you won't go to jail & have to hire an attorney, etc, & it won't guarantee that your partner will back you in the event that this does happen.

I don't think that this is all that much to do with what you have or haven't done. It seems to me that the mother is manipulating the girl into 'choosing her side'. And yes I know; this will NEVER be admitted out loud, ever. Not by the mum or by the daughter.

Been there, I can relate very well.

We have also been in that situation where the oldest daughter stayed with us for a longer period of time and all of a sudden the youngest one didn't want to come to our house anymore. She came up with some reasons that weren't very substantial. It really was a loyalty issue; she felt she needed to do right by her mum by picking her mum's side (mum feeling rejected/betrayed by the oldest daughter). But she never said anything to that effect of course, it is all very subtle. A simple example; mum might talk on the phone to a friend, knowing youngest daughter is within hearing reach, and say something like: "Oh well, I had planned a nice weekend for the kids but oldest girl is staying with her dad so why do I even bother?"
How can a 10 yr old not have feelings of guilt over that? She receives the message loud and clear. So she denies her own needs and focuses on her mum's; which means she will want to stay with mum and not visit dad. So she'll tell her mum she's rather staying with her, and mum might even reply that she doesn't want to keep her away from her father, she should really go. She might feel like her mum is being so supportive of her, and always encouraging her to visit her father. She will believe that it really is her own choice to not want to go to her dad's place. Pretty nasty stuff.

And then she has to give you guys an explanation of why she doesn't want to come and stay, so what does she say? She'll have to come up with something so she'll pick something obvious that is hard to argue with (because how can you argue about her feelings being valid or not?)

Going to court and getting lawyers involved; sure it's an option; but if mum plays dirty (using manipulation and guilt) then I don't think that going down that path will help your fragile bond with your youngest SD. I think it is better to try and reach out to her first. She is being made to choose, resist temptation and do not pull the rope back!

It worked for us. Instead of discussing the reasons that she told us for not coming to stay with us we left that alone and took a different approach. We showed understanding for the difficult situation she was in, not that she was admitting that. But we told her anyway that we imagined it can't be easy for her and that we understood she felt the need to stay with her mum more. Once we stated that as a matter of fact, she knew that we knew. So she didn't have to make up 'reasons' anymore either, that took the angle out of that one. But it didn't mean that the situation changed; we still saw her a lot less. What we did do was try and help make it easier for her to come to our place by being more flexible. For example when she says she doesn't want to come and stay for the weekend you could suggest she can still come for dinner on Saturday night (not sure if you guys live close enough to do this). And if that doesn't work out for her Sunday lunch would be great too. That way you actually help her negotiate a very difficult situation with her mum where she can still spend some time with you guys as well. You need to help her to keep in touch with you guys.

I don't think you are an evil stepmom, have you heard of the book Divorce Poison by Richard Warshak, it will help you a lot I think.

Hugs to you and all the best; hang in there!

I really feel for you. You are up against alot there, all I want to say is you sound like you're doing the right thing and getting little gratification back for it.

Being misunderstood is my biggest heartache with these situations and children can be quite clever at creating the drama, leaving us, the rational adults, nervous wrecks! Mother's that create loyalty issues are ruining their children's lives, it makes me so upset as I am in a similar situation. The biggest blowout we had to deal with with our teen resulted in a 'she doesn't like me' situation and that is low, really low. 'Tell me son, what gives you a reason to think that, I dunno, she just doesn't....' Never mind taking responsiblity, or apologising, challenge him and it's my fault..... So then the parenting stops again... I'm not sure there's an answer, other than the strength of you and your partners relationship is crucial and yes, definitely let him parent the boring details that may save you some grief.

Thanks everyone for the replies, sorry it took me so long to reply back.
I appreciate all of your input and since posting this I have taken your comments into consideration. I no longer stay alone with my youngest SD nor do I ask her to do anything. I leave it all up to Dad but that doesn't seem to help because he doesn't enorce any rule on her. I guess I'm trying to stay out of anything that involves parenting his kids even if at times I feel the urge to say something. It gets frustrating when she comes over and is rude to him like telling him to shut up and such things, but I guess of that's how he likes it, right? I'm starting to feel as if I'm nobody in this relationship and I don't mean that because of me not parenting his kids. I guess there's more trouble in paradise than I thought. Either way thanks for every thing!

Your guy's daughter is in the driver's seat.

When she decides to get rid of you, & she will, she'll call Child Protective & say that you did something to her, & Dad won't swear that you never have been alone with her.

You cannot change their relationship, & their relationship, for you, is a disaster in the works.

I wish you the best.

Being a step parent is a life of misery. I have a 15 yr. old stepson whose mother sent to live with us at the age of 12 because of his constant behavior issues. Well, now I see why, he for sure would have interfered with his mother's new marriage, and created nothing but havoc in the home. She kept the two girls age 17 & 13, according to them their problem brother is "all my fault," because I am the wicked step mother, and expect truth and accountability behavior, which the father does not expect. I am going to tell you now thinks are NEVER GOING TO GET BETTER.The father refuses counseling, and the son has been through 2.5 counselors, with two recommendations for psychiatric + counselor team counseling, which the father, lamely puts it as, I CANNOT MAKE HIM GO. This man has NO BALLS when it comes to parenting. There are millions of men out their like him, and it will always be your fault, for ever. These kids grow up to become mean, adults who believe in entitlements. Do not have children with this man, your child will suffer, your partner will always suffer from some kind of guilt syndrome and place these kids first.