Using the excuse that she has no one else is just weird. Like why are you trying to pity someone into hanging out with you? It’s like she knows he would say no otherwise so she is trying to use leverage. As others have said is she truly just wants friends she should have invited you both. Also the fact she’s rude to you??? I’m not sure what boundaries you have discussed with your bf but I know my bf would immediately drop ANYONE who was rude to me and vice versa.