I figure about 10 to 15% of the people I meet are assholes. I don't spend time with them; I don't allow them to get power over me; I avoid them. I can see no reason why you would want to spend time with her, and if somehow a poly family formed with her in it, she would just make people miserable.
I would forget about making her love you or worrying that if you could love her things would be better. She is unlovable until she gains some maturity and some significant personal growth.
My suggestion is to keep your boyfriend (bf) at a bit of arms length until he resolves things with her. Tell him that you have tried many times to be friendly with her and you are tired of being snubbed. When she starts being nice to you, then you will reciprocate.
Good luck. Rick