Hey guys, so I've known this girl for about a month now, and we've made out a few times (fwb I guess), but each of those times we were interrupted by something so I wasn't able to escalate much further than kissing. Last night, I was able to isolate her in my bedroom during a party where we were alone and pretty much secure (the door was locked and nobody was going to disturb us because they knew what was going on). I'm a fan of the DiCarlo escalation ladder and I skipped all the intro shit because it wasn't necessary and I just go to the escalation ramp. At this point I should note the girl is pretty drunk but obviously into me, very passionate kissing and shit, and we're on my bed, she's on top of me. So I get to step 14 on the ramp (Direct Vaginal Stimulation from Behind) and am able to get my hand inside her panties but her shorts are so fucking tight that I can't go any further than her ass. They were like those denim booty shorts that girls wear. I'm like shit what do I do, so I try to undo her belt to get her shorts off so I can do it more easily. But she stops me. She stops kissing me and literally says no. I ask her what's wrong and she says she doesn't want to seem like a slut. I tell her that I don't think she's a slut but either way she shouldn't care what I think. So we continue kissing, and I try again, but again she says no. I try another time after and again she stops me and says she isn't in the mood. Which really confused me because she was basically grinding on me at this point, and I could get my hand on her ass without her saying anything. I stopped trying at this point, because honestly I had no idea what to do. We're both 18 and virgins, if it matters, and yes she masturbates/has had orgasms before. I've never had a girl straight up tell me 'no,' is this normal? What would you have done in this situation, and what should I do the next time I'm able to isolate her and escalate? Thanks guys.