Well, my first words of advice: Dont ask for help on a video game forum. I dont have to go into details, I think you'll understand.
And yeah, make sure you know for sure who this person is, you dont want it to be a 45 year old pedophile.
So, if its a real 17 year old girl, just go with the flow, getting a gf is easy if they like you. Just be nice to the person.