It sounds as if you have been trying everything reasonable. I agree having another vet check her out would be good...(and be careful of the bite I got between two of my cats in a squabble and ended up needing massive antibiorics from a tooth scratch that would probably not have gotten through Jack's fur!).

My sister had a cat that attacked the way you are describing. One day it climbed in my lap, rubbed on my cheek and bit me through the lip. Well, I screamed, chased the cat, caught her and bit her in the ear (pinched, really...I didn't draw blood) until she squeaked. The cat never attacked me again and when she was ill I was the only one who could pill her without damage. She actually became pleasant with me. Now, I don't know if you dare to try this with your cat, but maybe some reaction that gave her back a negative consequence and re-established her place in the colony would help. If she can be brought to see you are a dominant member of the colony she will respect your "kitten" too....

Good luck!