Quick Summary: I met this girl through an online dating app, we hooked up twice. She caught feelings, now I can't get her to back off.

Long story short: She wanted a relationship, I told her I was not into that and that I was only looking for a casual thing. She said she was fine with that, but after we hooked up the second time, she said she was not ok with it and wanted a relationship. I said no and proposed being friends (thought it was the nice thing to do), but she seemed to ignore it and became very clingy. I then told her that she is starting to get weird and creepy by texting me so much. She would send these texts where she would ask me something, I won't reply and then she would start answering her own questions and ask me things like "why am I so into you". After about a day of her cooling down with the texts, she then proposed we be friends with benefits, but after seeing how attached and clingy she got after just 2-3 dates I told her no and I just wanted to be friends.

Conclusion: It almost seems like the more I don't respond to her, the more she gets attached and if I respond to her, she thinks things are getting "normal". She told me she is used to getting what she wants and when she can't get it, it motivates her even more to get it. I feel like I am in a lose lose situation here. What do I do to get her to back off and leave me alone, it seems like she doesn't get that I don't want to be with her?