Female Cats Do not Like Each Other:(

I have 2 Female Cats, one is 9 and the other Is 7 months old. They have never gotten along, although they seem to do fine with the other cats, that are all male. With my 3 other males Twinkles, my 9 year old Female is fine, But with Mimi, She always Hisses at her when she come near her. Mimi is trying to approach her, but Twinkles won't let her. They do not do anything either than Hiss, But I want them to get along. Do you think that Twinkles could still be upset about the loss of our female Tabby Ginger who passed on? Any suggestions would be helpful. Thanks

I just wanted to say I have two females also, and they are not exactly buddies either. My vet told me that females can be very territorial, and that they don't always get along with other females. I wish I had chosen a male sometimes, but then I look at Cymone and I can't imagine not having her.

I hope your two work it out so they can at least be "civil" around each other. Thats where we are now, no fighting, but no playing either. Basically they just ignore each other.