Our two cats are fighting like strays
We have two cats, male and female that just starting fighting like two strays. Both are indoor cats and we've had them both for about 7 years. We moved into a house a year ago and our neighbor has a few outdoor cats. One day the neighbor's cat jumped up on our front step while our cats were sitting in the door. Our female cat tried to lunge for the neighbor's cat but of course hit the screen in the front door instead. So since she couldn't attack the neighbor's cat, she instead attacked our other male cat. And they fought like I've never seen them fight before. It was really like two stray cats fighting. We separated them and were finally able to put them back together until a couple weeks later I accidently stepped on the male cat's paw and he let out a scream and she attacked him again. Now, we can't even keep them together or else they fight like two strays - howling and everything. The vet says its displaced aggression but didn't give us much help in trying to get them to live together again.
Is there anything we can do to get them to be friends again? We've tried the vanilla trick so that they both smell the same and we've even tried waterless shampoo baths to make them smell the same but that didn't help. We bought leashes so that we could have "supervised visits" but they still howl when they see each other. The vet even gave us pills for the female to calm her down (pregnancy hormone) but that didn't seem to do anything. The good thing is that neither of them seem to come out of the fights with any scratches that I can see. Oh yeah, my wife is also pregnant. I'm not sure if that is having an affect on our cat's behavior. Has this happened to anyone else? I'll try anything at this point.