Y'know what's funny? I find that when a girl brings an issue to you to you, and you give her exactly what she wants, she usually ends up not knowing what to do with herself.
Perfect example: I was dating a girl one time and told her that I wasn't ready to introduce her to my friends. So, of course, she went on and on about why that wasn't fair, and asking if I was embarrassed for her to meet them, etc. So, one day I finally said "y'know what? You're right, I have no problem with you meeting my friends at all. In fact, we're having a get together on x-day, you should come through." A few moments later, she said she was now nervous about meeting them because she was afraid they wouldn't like her and she'd embarrass herself.
The point of this story? GIRLS WORDS MEAN NOTHING.
I've been in this same situation before: girl invites me over or comes over to my place and gives the whole "we're not having sex" speech. Anytime I get this speech these days, I know we're going to have sex. Why?
SHE BROUGHT UP THE TOPIC OF SEX FIRST
If she brings it up, regardless of if it's in a "we're NOT having sex" or "we ARE having sex" statement, the reality is the phrase "HAVING SEX" is still being put out there, which means she's thinking about it on some level. So, why would she give this statement to you? Several reasons:
1. She doesn't want to come across as easy
2. She doesn't want you to think that you can just use her for sex
3. She wants to believe and feel in her mind that you like her for more than your body
That last one is key - she wants to BELIEVE and FEEL that you like her for more than her body. Even if it's not true, she wants to BELIEVE and FEEL that she is worth more to you than a fling. The secret, then, is to make her feel like you have more of an interest in her than her body.
SO, here's how the game is played my friend:
1. When you go over there, she'll probably reiterate her "not having sex" stance. YOU, my friend, need to come back with something for her - something she's probably never heard a guy say before: "With all due respect ma'am, so far YOU'RE the only one that's brought up sex, not me"
2. You do NOT lie to her by saying you don't want sex with her - that's how "nice guys" mistakenly end up in the "friend zone." Nor do you say you want to out and out bang her - that's how you end up not getting the lay. What has worked for me is saying the thing I mentioned in #1, followed by: "Look, I'm just happy to be in your company. If it leads to us doing other stuff, then great, but if not I'm just glad to spend time with you." The reason I phrase it like this is to let BELIEVE and FEEL that I'm going to have the SAME good time with her whether we have sex or not. This way, she doesn't equate my good time with her solely on whether or not we have sex. Ironically, it also lets her know that if we DO have sex, that can also be added into the "good time" I'd already be having with her.
3. After you give this little speech, BACK OFF. Let HER come to you. Talk to her like you normally would but don't initiate any touching - you want her to FEEL like the speech you just gave is TRUTHFUL by not making any sexual moves on her. Let HER be the first one to break that barrier by touching you on the shoulder during one of her stories, or hitting you with a pillow, or sitting next to you on her bed. Heck, you can even play with her a bit if she does this - like, if she sits next to you on the bed, you can say something like "whoa there, missy, I see where you're going with this, I need to be wined and dined first, lol!"
4. Assuming you've done these things, one of two things will happen. Either she will initiate touching, and you can figure out how to escalate to, at the very least, getting some make out action; or, she won't do these things and you'll leave - but, by actually leaving and not trying to do sexual stuff, her lil' hamster wheel will be running, pondering the things you said AND if maybe she was wrong in saying what she said. Which makes the next invite over to her dorm an almost-guaranteed lock-down for sex.
Regardless, if at any point she starts saying "no, I don't think we should," BACK OFF and don't make a big stink about it. The less upset you get about it, the less you'll seem like you're trying to force her to rush into it and the higher probability of her agreeing to sleep with you. On the plus side: the majority of females wouldn't invite you up to their dorm room if they weren't thinking about hooking up with you on some level, soo... yay!