You CAN get them to stop (I've managed it) but it takes time, perseverance and a lot of trips to the laundrette!
- spay, this is the first biggest thing to do (assuming you haven't already), an unspayed rabbit will just mark everywhere, showing where they're territory is, this will include your bed!
- don't give her attention when she does it, either negative or positive attention. Rabbits thrive on attention and anything that gets it for them they will repeat! This includes getting out of bed and immediately feeding, mine used to pee on the bed while I was in it to say 'get up mummy, we want breakfast!'
- don't feed treats or any food on the bed, this will make her associate the bed with food, something else that can trigger the 'give me attention' weewee!
- make sure she can get down. We had a lot of trouble with Mischa peeing on my bed, turns out he struggled to get down and just wouldn't. If he had to he would launch himself off, splat! So we built him a little ramp.
- tarps! A big tarpaulin works well to protect your bed, it also makes it less soft under their feet, something which i think triggers their 'i need the loo' reflex, and obviously it's a lot easier to clean up off of.
After about 6 months to a year we eventually got there and now mine come up on my bed and we haven't had an accident for some time (though every time I say this I spend the night worrying that they will prove me wrong!)