<human>: Can you succinctly summarize the text in 1-3 sentences?

Please tell me if this is the wrong place to post this and suggest the right one. 

My boyfriend of 5 years and I broke up two years ago, this year I have been dealing with the feelings I still have for him and the regret of the lost relationship. Trying to get back in touch with him and expressing to one of my best the regret I feel from losing him. 

Said best friend and I have been very close for seven years she was with me at the beginning and end of my relationship with the ex. I found out a week ago that he had contacted her, I asked her to pass along my information and express my regret about the end of the relationship. 

To the point she comes over the other day saying that she hung out with him, I ask if she slept with him (well because she sleeps with a lot of people) and she responded yes. 

Am I wrong to be end a friendship over this? She knew I had feelings for him still and wanted to fix things yet she made the choice to sleep with him regardless.
<bot>: My best friend slept with my ex of two years whom she knew I still have feelings for. Am I over reacting by ending or friendship of this?