How do I get over my obsession for this girl?

[john]

Uhh dude? Not to sound like a jerk, but you've never even met her. I realize you've probably talked extensively and stuff, but it's just not normal to be that committed to a person you've never met in person.
Anyway, I have a thing I do when I feel like I need to control my feelings.
I stop talking to them. Sometimes, this is a bad thing, I literally stopped talking to a girl I loved deeply for three years, but that's an entirely different situation. If you stop talking to them, but make it clear to them you don't want to be doing this, they'll probably be okay with it.
However, considering she blocked you from everything, I don't think she wants to talk to you. Just focus on it a little less and a little less every day, and you'll eventually get over it.