Hey, this sounds like a really tough experience.
I don't know if you are looking for advice, but for what it's worth: GIRL1 is throwing up massive red flags. She doesn't respect your boundaries. When you say "I don't want to have sex", she doesn't say "ok, I understand, no problem" and smile at you - the only OK response!
Instead, she emotionally manipulates and guilts you into sex. You know this isn't right - you posted in this thread.
I know you have feelings for her, but this woman is really bad news. Please take it from someone with experience in this area: someone who manipulates you, refuses to respect your no, and then makes YOU feel like an asshole for just respectfully asserting your boundaries, is NOT someone you want to be with.
This will escalate. If you guys start dating, eventually she will start picking fights over dumb stuff, trying to control you with tears and outbursts, and never respecting it when you try to tell her how you want to be treated. You will be miserable. Please run.