Carmen and Tosca can have a little spat now and again. Mainly because Carmen is a little snooty and thinks she is IT (well she is but so is everyone else)
.
Now and then I will hear a hiss and a growl from them. I'll find them having a stand off. Ears down ready to bat the other one. It usually happens when Tosca trys to play with Carmen. Carmen doesn't really "play" with anyone shes far to "civilised" for that lol.
I feed them seperatly now and make sure Carmen can have the time out she so loves. I can tell she feels a bit stressed sometimes with all the noise from the living room and the three cats sitting on "HER" furniture. It doesn't happen often and they are usually quite tolerant of one another (they are sisters after all) it's just when one of them steps on the others paws.
I might try using a feliway myself. Can't see it doing any harm!
*EDIT* By time out I mean letting Carmen go into our bedroom on her own for a little while to sit on the bed.