I once had a best friend for a few years. Over that time frame, several small situations where I felt she was taking advantage of me arose, and I just ignored them...never said anything to her, but after maybe 5 or six smaller incidents, we had what I thought was a BIG incident and I dropped her. Told her once on the phone, don't call me again, I don't want to be your friend.

And the point of telling you this, you're wondering? She never tried to make up with me or make it up to me and had she, I think we might still be friends. She would have had to try more than once, though...I was pretty angry! Were I you, I'd write the letter and try to explain things. Good luck.