Stuck In The Middle At Work!!

Ok, here goes:

I started working on reception in an office a few months ago. I really enjoyed it to start with and became friends with my colleagues including a girl (who I'll call Matilda) and a guy (we'll call Malcolm). Malcolm and Matilda are both around my age (most of the people in the office are older) and so it was natural that we would be friends. At first everything was fine and although I was aware that they were close and that they had sexual chemistry it never interfered with my friendships with either of them as I tended to spend time with them seperately.

This all changed however when Matilda came back from a holiday and decided that she was no longer speaking to Malcolm. Apparently something had happened with Malcolm and a friend of hers although she has always been pretty vague about the specifics. Even this would have been okay but now every time Matilda sees me talking to Malcolm she gives me the evil eye and then later calls me a traitor. She n is trying to make me choose between them. He doesn't seem to mind when I talk to her and has apparently apologised to her but she still continues to ignore him. It is creating a bad atmosphere and has put me in a very difficult position...