Why do some people never leave no matter how much disrespect you throw at them?

I was in a relationship with a girl for around 5-6 months before we broke up (She got bored and went to find another guy) i was miserable for a month or two then i got detached but ever since then she has gotten way too attached putting in more effort than when she did when we were in relationship but she still keeps the other guy around? I openly admitted i don’t like her i don’t want her etc still she refuses to leave. I literally don’t give a fuck about her but now she’s not leaving stating that she can’t leave cause she loves me etc. This lead me to wonder even though i have openly disrespected her and called her names names (due to frustration in my personal life n of her entertaining another guy while still saying loves me) she refuses to leave why does this happen? Usually people leave after such disrespect and i don’t give her anything to stick around no affection no sweet words nothing. I blocked her but she still tries to contact me through other social media or through her friends. She already got some guy for attention and her needs then why can’t she just let me go??