Wow.
Sorry to hear about your situation but kudos to you for wanting to persevere where others may just give up and rehome the cat.
I don't have a lot of advice as I don't feel I'm experienced enough to provide much. But I'm sure other members will pop in and help more than I can.
My initial thought would be to try and keep the two cats separated, if possible. Can you let them have different parts of the house to themselves? I should imagine the introduction to a new cat isn't helping your already stressed bengal kitty.
Maybe ptting some feliway plugins round the house would help calm the bengal down? I had to use this stuff recently to calm my two bengals down- Widget had to stay at the vets for a few days and when he returned, Pixel acted like he was a brand new cat and hated him.
It sounds like (as you've identified) that your bengal is very stressed. Will she not go near you at all? What about toys/treats? Does she have a favourite food? How does she react if you just sit in the same room with her and go about your own business? Does she like toys? Do you have any wand toys (e.g toys on a stick and string) that you could try using with her? This might help her bond with you/get used to you.