How should I talk to this girl?

I would not suggest pushing it. I would suggest making small talk and not mention anything about the past pretend as nothing happen and start over with clean slate. Pretend as your just starting to get to know her again. It will take time and most likely she won't respond to you right now. Wait a little bit ans just be casual and work your way into gaining a stronger bond. I would keep the conversations up to "what have you been up too?" And such. Then I would try to start a bond by mentioning something like an inside joke or "ask if she still listens to this band?", "are you still doing.......?" Then you can establish a connection talk about things that only you and her kno just between eachother and exclude anything to do with the bad part of the past. Remind her of the good times. Don't look like your trying to push your romantic feelings to her just be a friend and try to gain her trust.