This thread!

A year ago we had days without a single post, now I can't keep up without constant page-refreshing.
She really isn't manipulative at all. She's a free spirit. She writes beautiful poetry, dances to music just because, and is just generally kind to people. Which is pretty rad. She's very empathetic and she's very compassionate. It's hard to define what sex is to her, she hasn't really told me, and I haven't asked. I don't know if it's just....fun? Maybe? Or if it means something more to her. She talks about it very casually.
Sounds like consistent behaviour and a healthy attitude. She seems very instinctive and emotional though, which means that you can't figure her out by what she says about herself. That's a receptive personality and with a girl like this you can't allow yourself any indecision or hesitation.
I liked the fact that you didn't described her as "reserved" or "shy", but that says more about your personality than hers and shows you are not interested in her out of apparent unavailability to other guys.
Actually, we met because I'm president of a club dedicated to BDSM, kink, and polyamory on campus and she's a member (but that's another story).
Like I said, I see a lot of conflicting thoughts about poliamory and such. You think it's not fit for you and yet you manage a club built over that very premise. You think you don't want to "share" her, yet you go out with another girl. I think you just need a bit of adjustment to the idea: you're like a guy who jumped in the water, felt it was cold, and immediately got out instead of waiting to acclimate.
I just don't know what to do. Should I suggest hanging out? Should I tell her how I feel? Should I just wait out the three weeks til break?
What break? from school? Keeping this thing unresolved is not a wise move. For your sanity and for her interest in you.
Everything I've read has told me to just steel my resolve and keep this up until she messages me first or comes to me directly asking for me to hang out, and if it never happens, it never happens, but those books are so douchey. I just don't know. I really appreciate all of your help, by the way. My goal isn't to steal her or anything, she isn't an object, and if she isn't as happy in my company as I am in hers, then I don't know that I want her in my company.
First of all, I'd be interested to know about these books. I'm always looking for new perspectives on relationships.
Specific to your situation, I think the waiting game is a mistake if you are not seeing other girls: when you have a relationship with a girl (whatever type that may be) and you revert back to hide and seek games through texts and phone calls (something you do when you are starting to know someone else) that's actually creating useless obstacles for yourself. If you keep doing this, all the ground you've covered through the time you spent with her will go to waste and you will find yourself back at the starting point.
Edit: So, update. I ran into her while I was getting coffee at the library and we stopped and talked. She immediately asked me how my date went and seemed to be kind of jealous.
This is good but she already knows she can get to you through jealousy. Jealousy is a tricky thing: it can revive an interest, or killing it completely. Since she is part of a BDSM club she may have a complex definition of pride: considering she is into poliamory also and she is excited by feeling "jealousy", showing her you are dating other girls may work. At first. Then she will face you again with a situation similar to this over and over until you will do something completely out of character and she will have "proof" you are completely into her. Then she will loose interest.
You need to keep your behaviour consistent, otherwise girls (and people in general) will use that against you.
Same thing when I mentioned how I was spending Saturday afternoon at the movies with a female friend. I, in my infinite wisdom, was high at the time (she was aware of this, we laughed about it) and I asked her about the other guy. She got kind of defensive.
I'm not entirely positive on this one, but I'd say she is fishing for validation. She wanted to see your hand before showing hers. This is a strange reaction. This reaction makes me a bit skeptic about the way you talked about her in your post.
In an awkward sort of way. I.e. a lot of false enthusiasm which is uncharacteristic of her I think I've figured it out. She has feelings for me, but those feelings are not equal to the ones she has for the other guy, and that's fine. It isn't a contest. But, I don't need to wait around. What I'm going to do is to just go about doing my own thing and if she ever frees herself up, great, and if not, fine. I don't need to wait around for it. I can be spending my time with people who reciprocate how I feel and don't have feelings towards someone else. I don't need to fall into the pitfall of getting hooked on one person.
You are clearly conflicted about your own behaviour, as these last two sentences show and contradict each other: on one hand you want her to date only you, in the meantime you want to keep dating other people. That's the purest form of a double standard if I ever saw one.
If she has self-esteem issues, it MAY work: but if she is manipulating you for validation, as in "I will now show the world that I can convert a guy from poliamory to monogamy, because I'm such a wonderful, mystical creature" as soon as you'll back off from this attitude ("I can't date other girls, but you can't date other guys") like all of a sudden you stop dating other girls to show her "she changed you" or "how much you love her", you'll loose her.
One more update (and I don't know if it's in poor taste to dredge this up again, so if so, I apologize sincerely): I'm thinking of sitting her down and setting boundaries by explaining why it is I'm going to have a hard time being friends and why it might be best to just go our seperate ways.
That's what I also was suggesting and IMO it's the best way to handle it.