She sounds manipulative....and I think all kids have the potential to be..if you let them....you have to put your foot down and let her know that this stuff doesnt work..and she wont get what she wants that way..it may not help with her doing it to aunts etc.. but will help with her not manipulating you..
I wouldnt have switched weekends with SKs missing Bmoms birthday because she threw such a fit..it gave her exactly what she wanted..gotta put your foot down..its hard but you can do it..she displays this behavior because it is tolerated,she gets attention, and gets what she wants..

5inall hit the nail on the head.

Often manipulation works because those being manipulated & used are so busy "putting out brushfires", dealing with the details & consequences of each episode that they don't have the time or the perspective to see it as a system & put a stop to it.

If you can keep someone off balance, defending herself from accusations or even just hints of some kind of inadequacy or lack, that person is absolutely unable to take control of the situation & exercise any authority at all.

Tail wags dog.

Yes, I do tend to agree that it is a form of manipulation... I believe she learned a lot of this during her parent's divorce (apparently it was pretty nasty.) Another thing that she does that bothers me involves calling BM when she doesn't get her way. If she asks me for something and I don't agree to it asap she has her cell phone out calling mom within 2 minutes flat. And no matter where I am she is certain to come to me to show me that she is on the phone.

Last week I was working hard on getting her involved in gymnastics. Considering she is on a waiting list for gymnastics, we were discussing the possibility of (for this session) letting her do the county cheer squad that she did last season but ONLY if they would let me be the assistant cheer coach. (The current coach is not very professional and I'm fairly certain that I would be able to keep the cheerleaders on task. I was a big help last season and the cheer coach had asked me to assistant coach but at the time I had 3 kids in boy scouts on the same night and couldn't help...now I can.) I had mentioned to SD that there was also a cool hip hop dance class they were holding on Wednesday's that would cost a mere $3 a week with NO other costs...and if she would be interested in doing that along with one of the big activities, I wouldn't mind taking her.

The next day I was cooking a roast and she complimented me repeatedly on how well it smelled. (It was pretty awesome, if I must say so myself.) At almost serving time, she stopped me and asked me about activities again. She wanted to know if, since I was willing to let her do 2 activities, if I would allow her to do cheerleading AND gymnastics. I told her I was sorry but those were the 2 expensive activities that involved travel across state and competitions. The hip hop class would just be a simple "one hour a week" thing that cost only a couple of dollars...but getting her involved in the 2 BIG activities would take a lot of time, double the money and double the travel. She walked out of the room, and just as I expected she arrived within a minute with her mom on the cell phone. She handed the phone to my stepson who was doing homework in the kitchen and then walked up beside me as I pulled the roast from the oven and said "Something smells weird..." She then looked to her little brother and said "Is that YOU that smells weird?" She then left the room.

Well, needless to say, my feelings were hurt. But I'm the adult here...so I stopped for a minute and thought to myself what my course of action would be...Five minutes later I said "You know, honey, I've been thinking...I'm a big sized girl. I've never been a cheerleader and I don't know the first thing really about being a cheerleader. Besides we didn't sign you up for county cheer squad this session because it was so unprofessional last session. So I think we'll just have to focus on the waiting list for gymnastics." She backtracked and told me how great I was and that maybe I would do a good job...but I stuck to my word. "No, let's just focus on gymnastics. That's what you need anyway if you want to get your backflips down for high school cheering." She was more disappointed than ever at this point and barely spoke to me the rest of the night.

I may have been wrong in the way that I dealt with this but to tell you the truth I really am not a cheerleader at all. I was only willing to do this for her...And I really felt that I needed to say or do something at this point.

Manipulation really is a big thing in my home and it's very disturbing to me...in part it is disturbing because I think to myself that I am dealing with a child and apparently this is just a thing some children do...so does it warrant some kind of consequence? I question myself regularly. It's not a good feeling.

In my home if I feel someone is trying to be manipulative (we have 3 kids) I stick to my answer...and I call them on the manipulation...That is just what I do, some might think it harsh...I feel it helps though to verbalize the attempt of the child to get what they want..ex..I know you feel sad (lots of tears) and you think that tears might help you get your way..but it wont..the answer is still no and that is all there is to it....(normally the tears dry up real quick:)
we havent had a big issue with this in our home but I think it may be because of the way we react to attempts to manipulate...we refuse to allow it...

Instead of questioning yourself, question her. Turn the tables to make her see it is unreasonable to expect everything. Point out the manipulative behavior and how ugly it is. And make her take inventory of all the things and wishes she might not get just because she behaves that way. What you did can be a prime example. Then make her try to imagine not having the things that belong to her and not doing the things she's been able to do. Make her realize what real misery could be and her faking in attempt to control people is the wrong road. She'll get the message.

I think that all kids have the ability to manipulate if you let them. I have found my self giving into manipulation at times.

The key is being strong. Think before you tell your child if they can/can't do something or have something. Once you answer then you need to stick to your answer no matter what they may say to try to convince you otherwise. If you change your mind they will come to think that they can always do that.

You also need to let your relatives know that when you say no then it is no. Do not let them do things for your kids that you already said no to.

This is a classic Drama Triangle situation. The child is presenting herself as a victim, her aunt and her friend's father are the enablers/rescuers, and you're the persecutor. It's a dysfunctional pattern, and needs to be called out, at least in your mind, every time it happens. The good news is that you have the power to end it. You can step out of the persecutor role by refusing to accept the guilt that your SD tries to impose on you. It's not easy, especially if there are lifelong behaviors that have been learned, but better to start now than have your SD grow into an adult who perpetually sees herself as a powerless victim.

There is much information online about this. I've included one link below.

Blessings.

Here is a link that might be useful: The Drama Triangle

Thanks for all of the feedback and advice, everyone. You have been VERY helpful! Although no one seems to be questioning this, I do want to make it clear that I do love my stepchildren with all of my heart...I just find it hard to say "no" at times, especially when they call mom when they don't get their way. Of course, it is much easier to say no to my biological sons but I have to realize that I can't JUST say no to them. That is so wrong and is NOT fair.

Fortunately, I have a husband who supports me in NOT allowing the kids to manipulate me. He is very supportive of me and of any way that I deal with individual situations such as this or anything involving the kids for that matter. He trusts my judgment, which is a good feeling. It wasn't always this way...there was a time that I had to question whether he felt I was being unfair but after 4 years those issues are a thing of the past.

I need to educate myself more on this...and I greatly appreciate the advice and links you all have given me!