Cat's not getting along

My fiance moved in with me about 2 years ago. I have 2 cats, M/F, Buddie and Girlie. She also has 2 cats, M/F, Jack and Chainsaw. Buddie and Girlie do not get along with Chainsaw. She is about 8-9 years old, female. She is also the smallest. She basically lives on our kitchen counter. 2-3 times a day we have to carry her to the bathroom where the litter boxes are. Feeding time is no problem. We let her hang out in the bedroom when we are home since we don't let any other cats in there any more because of my alergies. But any time she tries to venture out to other rooms she gets trounced on by Buddie and Girlie. Jack too but he just wants to play.

Any ideas?

might have no other choose bet to always keep them separated.

Is this a new development or have they not got along for 2 years?

If it's new a vet visit is in order to make sure she is not sick.

If they've never gotten along, you will need to reindroduce them http://www.thecatsite.com/forums/showthread.php?t=67321

Always been like this.