Constant phone calls, emails, etc are only going to remind her of everything that's bad about you and why she is no longer your girlfriend will remain and easy question to answer. I of course often find myself in just this position. You break up with her and she just has to keep calling, emailing and trying to break into your place to get back that one special pair of your undies...oh wait..maybe that's a story for another thread
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Leave this girl alone and for CRAP's SAKE do not buy her another animal.