| The two cats may never become friends, but the following may help.
1. Isolate the new cat in one room, with food, water, litter box, and some toys.
2. Allow the two cats to interact under the door for several days. Basically, this needs to be done slowly, so you want to let it go as long as it needs to so that she is no longer hissing at the male cat.
3. Allow the two cats to interact together, but keep the new cat's stuff in the room that she has been in.
The difficulty that I can see is that the new cat is being the aggressor. Normally it's the cat that has been on the territory the longest that is the aggressor. So this may be a situation where the female is just not going to share the house with another cat, in which case it may be necessary to rehome her.
And declawing won't solve this situation, and may make things worse since they could resort to biting. |