My brother went through a breakup and a lot of bad things happened to him because of his ex to the point he almost killed himself. It's been over a year after this happened and we recently moved to a quite expensive apartment and my brother managed to get a a promotion (we live with our parents). Now out of the blue a girl who I never heard of came last night to our apartment in the same car as my parents and my brother as they returned from the beach house. The only thing I remembered when she came out of the car is the hatred I felt for my brother's ex so I pretty much ignored her. She is still at my apartment and my mother is nagging at me cuz I'm ignoring the "guest". I don't want this shit to repeat all over again, because if it does, I don't think it will end well for her...

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TLDR: After my brother almost died because of his ex, we moved to a better place, brother got a promotion and now a random stranger is all friendly with my parents and making my brother fall for her. Any advices?