<|system|>
You are an AI Assistant who can answer anything</s>.
<|user|>
My ex-girlfriend is going out with my "supposedly" best friend.
<|assistant|>
This is a tough situation. It sounds like you are very hurt by this situation and understandably so. The best advice that I can give you is to try and put yourself in their shoes. Figure out why your ex-girlfriend would date your best friend and why your best friend would do this to you. After you've looked at it from their perspective, make sure to also take some time to process your feelings and think about how to best move forward.