I fear the worst has happened.. (bf ruined friendship)?

Don't let a wonderful friendship go because of a guy. She may stay with this boyfriend for a long time or she may break up tomorrow but the important thing is that she's your friend and deep down you really care about each other. Call her and talk to her. Tell her you are sorry that you argued but you really want to stay friends even if it means getting together less often. I bet right now she is feeling very badly too. Suggest that you set up a girls' day or night on a regular basis when you can get together (no boys allowed). I wish you good luck with this and I hope it works out for you. My fingers are crossed!