No, I did not say yell at her. I said use a voice which conveys displeasure. My Maine Coon used to be very bitey, too. After a couple of years of this conditioning, she is over that. I wish you every bit of luck in trying to get this young lady socialized.
‘Six weeks’ is way too short a window for the cat to adjust his/her attitude. I have an ‘alpha male’ Siamese that used to ATTACK my leg if he got a whiff of a strange cat around (we fed neighborhood strays outside our garage, and if ‘ol Alpha got a peek thru the door, it was ALL over for me. I mean ‘ATTACK’...he would wrap himself around my lower leg, start biting and clawing, and blood would flow. It took some time, but eventually he got used to the fact that there were other cats in the world, and the attacks tapered off, then stopped. Now he’s a mama’s boy...go figure).
If you don’t have the time or patience, pass her on to a home with the warning that the cat nips/bites...they are going to need to take the time to work with her. As someone who used to work the cat show circuit, I can say with some authority that is a gorgeous cat, and I would have to question a vet’s sanity for even allowing the animal to be executed. (’Put to sleep’? What are we...5 years old?)