[hasrv4fun]

Is she spayed ? If not it could be her coming into heat as they will go brain dead stupid when they start.
If she is spayed, then I would go with the advice of limiting her space. She is old enough to hold it for hours and pen her if you must and take her directly outside and wait till she does her business then TREAT and praise, praise , praise, she should get it in a week or two.
I have 7 females and everyonce in a while I swear the switch must turn off cause they do something dumb. But never so dumb as peeing on my bed ! I would be hard pressed to tolerate that and you shouldn't either. Keep her off till she learns right.. It may have been a retalition thing with her doing that. She may feel threatened by some one or something in the house. Has there been any changes by who or what is there ? There are a lot of things that can trigger this kind of behavior.
I probably haven't helped you but if you pick a pattern and stick to it , you should be able to get her to go where you want..The key here is to be the boss and make her go where YOU want , not where ever she choses.