@shypshnius,
Hi,
So, given what you said, here's my opinion:
a) She might be a mean person in general, in which case you should stay away from her. She'll just continue to toy around with you, just to mess you up. I think this unlikely though. Anyway, you should break of all contact.
b) She might be annoyed that you sought to meet her again after she broke up with you for being too clingy. It's still a rather mean thing to do, but I reckon she's trying to get a message across that you seem to have problems understanding. The message being: She dumped you, it's over. If you really want her back (and frankly, why?), your best bet is to break of all contact, and show her you can manage without her. Move on.
Focus on other stuff in your life: your friends, your hobbies, your studies or perhaps your work. Get the girl out of your mind by any means possible, because accidentally asking her out for a coffee is probably the worst mistake you could have made in this situation (barring serenading her in front of her window, I suppose). Also, delete her number from your phone.