I would suggest putting a litter box in the bedroom and leaving a nightlight on since she could be having vision problems.
Brush her frequently to reduce the hairballs and talk to your vet about products for hairballs. There are also cat foods with a 'hairball formula' to help her digestive tract.

11 yrs old is not old for a cat. Has the vet diagnosed her with arthritis? Is she on any kind of meds? When was her last checkup?

I agree--11 is just a kid. My baby will be 21 on her next b'day, and she's a purebred (they sometimes have shorter lifespans)

anyway, if she's fine during the day, and does this only at night? It would seem she's crying out for attention. She doesn't like that you're 'ignoring' her (I'm not criticizing, of course you have to sleep). I really think it's a psychological problem if it's only at night and often on things she knows you care about. They're pretty smart that way. My cousins once had a cat who would ALWAYS pee in an open suitcase--he knew they meant someone was going away.

I guess, the only real answer is to confine the cat to a small area that's easily cleaned, overnight. Not a great solution, of course.

Otherwise, I have to admit, mine just went through a spurt of peeing on the floor, by the litterbox. She was pretty consistant, so putting half a plastic tablecloth down there, seems to have at least protected the floor. She does have arthritis. But I don't think that was the problem. I just noticed she's got some wicked knots on her back legs--have been working on them little by little for the past several days--and she's back to using the pan. I suspect the knots were pulling her skin uncomfortably and making it hard to get in and out. I have NO idea how she so quickly developed such wads, but perhaps you want to check your cat? I've also considered putting a 2 by 4 along the outside of the box (under the plastic tablecloth, of course), to make a step for her--but at the moment, don't think that will be necessary.

Hope you find an answer that works for you. Of course, the hairballs are an ongoing problem with long-haired cats. I find feeding a hairball forumula food and frequent grooming does help, but certainly doesn't eliminate the problem.

Annz and Azzalea--Thanks for the suggestions. She was in for a check up about a month, six weeks ago, because I thought there might be a UTI, and the vet says her hips are some of the worst he's seen (poor girl) so I could understand if she was just too slow to make it to the box when the urge hit but that's not it. She will pee right by the bed, in the spare bath, the kitchen, hall, all over the place. It is not a distance thing. I had a Siamese who would pee in my shoes every time I left overnight, so I understand about the crazy that is a cat but I am starting to think she is demented. I've considered jealousy, we were a one cat home for about 2 years, but we've had another for a year now and the behavior is only a few months old.
Believe it or not, my husband had the night light idea about a week ago so we have a little light trail through the house now --no luck. A neighbor suggested cleaning everywhere she's ever peed with vinegar so I will try that and give it some time but I may have to resort to confining her at night, though that will break my heart, I just dont know if I can take stepping in or putting my hand in another mess and there is one every morning--somewhere. The crazy thing is, she comes back to bed afterwards, literally climbing the comforter, since she doesnt jump well these days.

She may be relating the pain in her legs to the litterbox and is avoiding it. Even tho she uses the box regularly during the day, her pain may be worse at night.
Ask the vet for some pain meds, and please put a ramp next to the bed for her if her hips are that bad.

Did he x-ray her hips and did he rule out any type of disease in her hips?

BTW.......don't use vinegar for the pee areas. Once you use other products the enzyme products won't work as well. An enzyme cleaner made specifically for pet urine will give you best results.