You've never blown yourself out, until you submit defeat. Just remember: YOU are the object of SEX. She should be wanting you!! You create the frame in the conversation, and she has to comply if she wants to be with you.
So wait, you're in the same high school then?? Why are you opening her ONLINE??? Don't be a nerd, when you see her around, smile at her and open.
Anywho, if you're really opening girls from your high school online, then I would play the same game, "Do I know you?? I'm just being friendly, you don't have to be rude

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Another note on this, I think this is very popular amongst high school girls. It's just an immaturity thing. They want you to DLV to that comment so that they feel more popular/pretty/secure. If someone is rude just mock them in a playful manner. I hope this helps.