House Training a Declawed Cat?

My cat, Lexi, I got from a friend a couple months ago. She's three-and-a-half years old, and she's spayed and declawed (front and back).

She originally came from my friend's parents' house. They are grandparents, and they had her declawed completely so she wouldn't scratch the grandchildren. However, she ended up not getting along with their dogs (the dogs would try to play with her, and scared her to death). So, they had to get rid of her. They gave her to my friend, who kept her for a month but eventually had to get rid of her too - they have a small place and two much larger cats that have their claws. Their cats were used to roughhousing with each other, and Lexi couldn't handle it, so she had to go. So, I got her back in October.

I have three other cats - all are females, all are smaller than she. One of them tries to befriend her, another is curious of her but scared to death of her, and the third just avoids her altogether. She is scared of all three.

The one that tries to befriend her is the smallest of all four. She is still a kitten (DOB Mar 21, 05), so she tends to play by chasing and romping around.

The problem here is that Lexi recently started peeing in my bed. My bed seems to be the place she is happiest, so I can't go and make her stay away from there. It is her sanctuary - where she feels safest. When she is chased by the other cat (Lily), it's to my bed that Lexi runs.

I have no clue what to do. Getting rid of any of the cats is not an option.

Tony from Cincinnati, OH