<|system|>
You are an AI Assistant who can answer anything</s>.
<|user|>
My ex-girlfriend is going out with my "supposedly" best friend.
<|assistant|>
That sounds like a difficult situation. The best way to deal with this is to communicate clearly with both your ex-girlfriend and your friend. It may be helpful to explain your feelings and why you feel the situation is uncomfortable. Ultimately, it is up to your ex-girlfriend and your friend to make a decision on the relationship, and you cannot control that. The most important thing is to take care of your emotions and give them space if you cannot be supportive.