What a horrible thing to do!!! I can't believe she did that!!
You have every right to be upset and majorly pissed!!
Say whatever you have to say to her and get it off your chest and then move on....she's obviously not a friend and not worth wasting your time on.
And feel good about the fact that you've made great decisions for yourself and now have a great boyfriend and an awesome apartment!! You've done nothing wrong so screw her!!