Go for it hun, burst her little bubble and her small mind that goes with it. UN RESERVE her as a drinking buddy, (you are better alone than in bad company). THEN ignore her and get on with your life with your boyfriend who sounds as though you are really enjoying being with.
Another thought for you too.......I had a flat mate once when I was at uni, he NEVER used to buy loo roll or electric, he used to eat my food, use my shampoo, run up a huge phone bill and then it would take me ages to get his part of the bill off him................ so whenever he was there, I would take the loo roll out of the loo at 10.05 pm. (coz the shop next door shut at 10 p.m.). Perhaps you could try something similar - okay - pedantic as that may seem, but a little revenge is ALWAYS quite sweet !
Take Care and Good Luck.
Katie. x