I wish you could have tried this from the beginning.
I don't know if it can help now. They all have their 'mental picture' of all the other cats.

But I would try putting one drop of vanilla extract on the shoulder blades of everycat.

This makes them all smell the same to eachother.

This is great for introductions, but in your case, if it does work, how long are you supposed to keep it up? Jeez.

And I'd also try to get her to accept the most mellow cat in the house first, one on one. She may be overwhelmed.
Does she have a special territory? A bed, a room or a spot on the floor?

Try to keep the others away from her private spots.