Eight month old female cat very aggressive toward our other cats, and sometimes us.

My wife and I have 3 friendly cats, 2 older and one large male about 4.  All are fixed.  We brought in a neighborhood stray female over two months ago.  She was found to be fixed and healthy by the vet.  He estimated her at seven months old.  We gave her basically half the house to herself and have been trying most of the socialization techniques I can find on this site.  I have given her dozens of different toys and tried to get her to play but without much luck.  She seems agitated with her tail swishing about 95% of the time.  I literally mean all the time.  I've had cats for over 40 years and never had one this wound up.  You cannot pick her up or even walk by her safely if her tail is going.  As far as clipping her nails or holding her, forget about it.  She has attacked both my wife and I quite violently leaving deep scratches, and my wife is about done with her.  The only time she calms down is during the night when we have been letting her sleep on our bed.  At that time she can be very nice and even snuggle a bit so long as you don't upset her.

Worse yet, at the mere site of any one of our other cats through the double stacked baby gates she wines, hisses and gets even more wound up!  We have managed to keep them apart except for one incident which ended in a melee.  Fortunately no one was hurt in separating them.  I wasn't sure at first who the aggressor was but it's the kitten beyond a doubt.  Obviously she was never socialized with other cats.  She doesn't seem afraid of them, just wants to attack them on site.  To wrap up, as I mentioned my wife has had enough but I'm trying to buy a little time to keep working with her.  Is there anything that might calm down this wildcat or at least show a bit of progress toward socialization?  Thanks in advance for any advice.

Have you tried Feliway diffusers or spray?  

Socialization can be tough. I would definitely try the feliway plug in and spray (the plug in takes 30 days to kick in so the spray can get things started). Be sure to spray the area's 5 minutes before you put her in the room because it can overload their senses.

In terms of interaction, have you done the thing where you just go in and sit on the floor with a book or something and ignore her. No interaction from you and let her come to check you out on her own terms? From there sometimes you can move to putting a hand or arm out and letting her sniff and rub her face on you and go from there before you start playing with her.

I have a male Maine coon and he came to us a bit too early we suspect. He gets very aggressive and angry post playtime for some reason and often takes it out on us or his cat sister (not related by blood).

As a last resort you could try a short course of something like clomicalm or prozac or remeron and then work with her, using treats and the things I mentioned above before trying to let her meet the other cats you have.

Thanks for the advice.  I just bought the feliway diffuser and spray as well as a special collar.  I'll keep working with her and hope for the best. 

Keep us updated with how she is doing I wish you the best of luck!

Unfortunately, my best efforts have not been successful.  The "friendly cats" and the "unfriendly cat" will eat on either side of a baby gate for a minute or two if and only if both are very hungry.  And after a minute or two they are back to hissing and screeching at each other.  The problem cat has learned to occasionally climb over a double stacked baby gate and get into the main area of the house but immediately seeks out and attacks the first cat she sees.  And the attacks are vicious.  She also lashes out at my wife and I almost any time we walk by.  My feet, legs and arms are noticeably scratched up.  She will occasionally nuzzle against my leg or let you pet her but even those moments can turn to her lashing out on the drop of a dime.  She cannot really be trusted, ever.  My wife has given up on her and wants her gone. 

I have been using a feliway multicat diffuser nonstop in her safe room for 3 months now as well as the spray and a pheromone collar.  No change in behavior.  It's been 6 months now and other than the eating on each side of the gate there has been no progress.  My last resort would be medication.  My guess is it would have to be strong to do any good.  Does anyone have experience with such feline medications?

Prozac would be an excellent aid if you've tried everything else. It may also help to reset her and you may not need drugs after some period of time.