My cat hates my other cat what should i do?

Spaying may help. Signs a cat is is not spayed are that she will put her rear and tail in the air from time to time when you pet her back. She may become more affectionate and frequently groom her private parts during her heat. You could try separating them for awhile in separate rooms with their own litter boxes and food. After you don't hear hissing through the door, put up a screen door or stack 3 baby gates. Put their food on each side of the baby gate where they can see each other but not so close they become irritated. Then bring the food dishes closer together while keeping the barrier up. They may get used to each others scent and the idea of being near each other without hurting each other. You could get a cat enclosure and put it by a window so you'll have a cat door so that one can enjoy the smells and sights of the outdoors while the other one enjoys your company and the house. You could have them take turns this way so you don't have to live with the stress of them fighting. I commend you for trying keeping them. I am looking for a solution for my cats--I got a 9month old who I have had for a month, and she and my 7 year old neutered male do not get along. I am having her spayed next month and hope it will help. I notice she is more aggressive during her heat. Mating rituals for cats are aggressive. Indoor cats can go into heat year around and as often as every 2 or 3 weeks. I have heard about giving cats sedatives or anti-depressants for the aggressor or use Feliway. Also, try putting vanilla extract on the bases of their tails and between their ears to mask fearful pheromones. Put it on both cats so they will both smell the same. I tried the vanilla extract and the Feliway. It helps some, but it is inconvenient. I sometimes forget to put the vanilla on them and wonder why they are being so horrid to one another. Vanilla extract is cheaper. Feliway works for some cats and not others. Give them treats when they are ignoring each other. Try to distract the friendly cat with a toy when it goes up to the hateful cat. The hateful cat would just be glad not to have him in her space.