<human>: [M/17]

So me and this girl were talking for a while and both became really open with liking each other, but some stuff happened with me that I won't go into detail but we stopped talking for a while. Anyway we recently started talking again and I asked her if she still liked me and she responded by saying she thinks she does but she got a boyfriend just last week.

So now she knows I like her and my question is, how do I get her to leave her new boyfriend for me? I'm not asking for you to tell me that I missed my chance or that I should accept it cause I'm a pretty selfish and possessive person so I'm likely to pursue this either way.

Also I know I'm only 17 and I'm in my last year of highschool so it isn't really that serious but I'm genuinely upset with myself for not getting in contact with her again just a bit earlier because I really like her.

And I'm not actually sure if this is where I should be asking for help, but I figured I could get some good advice considering, well, who knows women better than women?

Condense the text into a few key points
<bot>: I like a girl and she kinda likes me, but she has a boyfriend all of a sudden, how do I steal her from him?