Why would she act so odd?

Ok. long story short she broke up with me 6months ago after a 3 monrh relationship. It was really lightning fast on 4th day moved together and everything else came superfast as well. She did not give me breakup reason and we didn't stay in contact. So to the odd part. She has a newr boyfriend and what I hear and see is that she is claiming I'm stalking her, she is seeing me everywhere every day, yet I Haven't seen or contacted her for tbe whole time. It bugs me becouse I am hearing this from more and more people. Its making me worry about her. Any advice?
Why would she act so odd?
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