The tail-attacking thing isn't always due to stress. My Cricket was rescued and brought indoors as a kitten. She took to the indoors like the proverbial duck to water. Months later she started biting her tail. The vet diagnosed her with feline hyperesthesia.

Feline hyperesthesia

We tried antidepressants and kept her in a cone for what seemed like forever, but she just wouldn't stay away from that tail. Finally the vet amputated her tail, and she hasn't had any more problems. Fortunately, she's never had seizures.

If Violet isn't showing any other symptoms (like "twitchy" skin along her spine), then it may well be stress-related, in which case the antidepressants may help her. But if cats are at all like humans where antidepressants are concerned, it can take awhile before there's any effect.