Should I give my kitty away?

I have a 2.5 year old (Kira) and a 11 months old (Mocha) kitties. Both female and spayed. I got the second one thinking it would be good company for the older one when I'm at school. But after 7.5 months of trying, they still don't get along. They fight sometimes and only once they did hurt each other (just a small cut, but still). The younger one is fine, but the older one seems unhappy and bothered by the younger one. Also, though not as important, my best friend can no longer come over cause he can't handle his allergies w 2 cats in here. It breaks my heart to give her away (Mocha, the younger one) but it just seems so unfair to Kira that she has to put up with Mocha. When I've had to leave Mocha at the vet for a couple of hours, Kira seems so happy and relax. I know of good ppl that will make Mocha happy so I know she'll b ok. So, what do you think?