Kinda late to the discussion. but I've been in this situation twice.
My second GF was 17 when she had her first kid, and we did ok until she cheated on me, so kinda biased there.
My Third GF was 20 when she had her first, but she was a nice girl, I helped as much as I could, we still hung out, obviously though, it makes that 10 times harder to go out at night, etc. because the baby has to be taken care of. So if that is important to you, you have to consider that.
I see nothing wrong with dating her. She's sounds like a good person who got with a bad dude, and is genuinely interested in you. Take a shot, you don't want to be looking back in 5 years saying "man I could have been with her".
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