<|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's really rough. It can be difficult to handle situations like this when you feel like you're on bad terms with the ex and the friend is no longer just a friend, but an ex-girlfriend. The best thing to do in this situation is to be honest and communicate how you're feeling. A compromise or understanding needs to be reached for your sake so try to reach out to your ex and the friend, and explain why you're feeling the way you are. They may be understanding and respect your feelings. Ultimately, it's up to you how you handle the situation. Do your best to make peace and move on.