Ex follows me around parties?

Everytime I see my ex in a party she follows me around and tries to get my attention although she has a boyfriend who is next to her.. what's the reason for her behavior? Secondly my exes boyfriend recently saw me in a party an he came up and spoke to me telling me he has no beef with me and hoped we were cool.. but the thing is I never had a problem with him? Could she be talking shit about me? Why doesn't she just stop following me around and stick to being with him?
Ex follows me around parties?
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