Hey all, I apologize for the length of this post and the fact that I'm not asking the clearest/most understandable questions, but the situation is quite hard for me to grasp so it's difficult for me to lay it out in a really concise manner.
I recently started my second year of college and I've been having some relationship issues with my best friend (we'll call her Elise). I'm in a fraternity and Elise (a senior) started dating one of the brothers in my house (let's call him Gustav, also a senior) around March of this year. They met at a bar and she started coming around the house pretty frequently. They entered a stable relationship that lasted a couple of months before being ended by Gustav due to a weird situation involving him getting drugged at a bar upstate and confronting the demons of his relationships over the course of his trip. While they were dating, I became pretty close friends with her. We texted relatively often and hung out frequently, but only in groups, usually when we were smoking or partying.
After the two broke up, Elise spent a few weeks single and then started hooking up with another guy in my house (let's call him Joseph). During this interim period between guys, I started to realize my feelings for her as we began hanging out more frequently and with fewer people around. She was quickly making her way into my closest circle of friends and I was actually almost to the point of asking her out on a date when she started dating Joseph. It caught me kind of off guard, because while I'm close to both of them, they didn't seem like a particularly great match. Indeed, my suspicions were more or less confirmed: the two dated for approximately a month, broke up (later, I discovered, pretty much because she wanted to hook up with Gustav that night), got back together again for a few weeks, then broke up again (I want to say sometime around early- to mid-July). She broke up with him both times. After talking to her about it, it's partially because they didn't work all that well together, and partially due to the sex.
So once Elise and Joseph were no longer dating (and I had returned from visiting home for a few weeks), we became best friends quickly. We were (and are, to this day) hanging out at least once or twice a day; whenever we both have free time we usually spend it together. We'll meet on campus between classes, hang out after school, do homework together, party, whatever. A few weeks after E & J broke up, we hooked up a couple of times. Both nights, we were both really drunk and the sex was pretty awkward. Over the next week, we had a few really long talks in which I revealed my feelings that I had had for her for a little while at that point. She said I was the most important person in her life, but she didn't want to date me because 1) I'm two years younger than her and she felt like it might be weird (Joseph is the same grade as me and I basically suspect that she's mostly concerned with the sex with regards to this reason); 2) She was worried there would be backlash/drama within the house if she started dating yet another brother after breaking up with Joseph. I wasn't happy about the situation, but I was glad to still have her as a friend and things continued pretty much as usual; and 3) She was worried that if we tried to date and broke up, it would ruin our friendship and potentially all the other friendships she has with guys in the house.
Not long after that (probably mid-August at this point), our frat threw a huge party at which Elise and Gustav had sex again. They did it on a couch outdoors on an upper floor deck late in the night, and apparently Joseph walked out to smoke a cigarette soon after they finished (when they were still incriminatingly lying on the couch cuddling). E & J haven't really talked at all since this happened (J was already pretty upset about being broken up with twice). Since then, E & G have started hooking up pretty regularly. On any given night, I can be hanging out with E and she will ditch me with little to no notice and at best a curt goodbye to go have sex. Even on nights when I'm working (I have a graveyard shift job), if I know that the two are going to hook up I find myself filling with rage and sadness. I feel like I'm fulfilling all of her emotional needs and spending all my time with her, yet she still has (largely sexual) feelings for Gustav and she lets those dominate her feelings for me as her best friend. She constantly tells me how important our friendship is and how I'm the most important person to her, yet she will ditch me at a moment's notice for Gustav even though she realizes how much it hurts me.
I still can't say exactly why them having sex bothers me so much. It's partially because I feel like I'm being used, but I feel like there's more to it that I can't put my finger on. I know that the fact that it is Gustav that Elise is hooking up with is far more bothersome to me than if it was some other random guy. The last several weeks Elise and I have had a number of intense talks about the status of our relationship, in which I repeated my feelings for her and told her how much it had hurt me that one of the reasons she said she wouldn't go out with me has totally gone out the window, as tons of brothers in my house now know that she is at least kind of back together with Gustav. Right now they are just friends with benefits, but I feel like she is trying to revive a dead relationship because while she still has feelings for him (and apparently they have great sex together), I don't think he cares about more than the sex at this point (he has some commitment issues after a string of crazy ex-girlfriends). I've encouraged her to talk to him about the status of their relationship, but she refuses to confront him about whether or not they are going to get back together because she doesn't want to mess up their current sex-only relationship, and because she is worried that if she pushes him there won't be any chance of them getting back together again in the long run (which I'm not sure would happen anyway). I really want her to talk to him...partially so I know where they're at, and partially because I feel like on some deep level I know if she tries to date him again they may stop hooking up altogether.
So basically, here's what I'm asking:
-Am I right to feel like I'm being used? Or do I just have to accept that she can't control who she has feelings for?
-Is it reasonable for me to be hurt that Elise and Gustav continue to hook up even though Elise and I spend far more time together (often alone) than the two of them?
-Is there anything I can do to change the situation? Ideally to make her realize that she may have feelings for me (because we would really, really work well together. We're practically dating at this point, minus the sex. I've had a number of people who know us both well ask if we're together), but if not that, to make the situation more tolerable for me? Every time I get ditched so they can have sex (in fact, even when I'm not ditched) it's like a needle to the heart. We totally have the rapport, the chemistry, the shared interests, the time spent together of a boyfriend and girlfriend...everything but the physical aspect.
TLDR Version
Best female friend knows I have feelings for her, continues to hook up with an ex boyfriend in what seems like a vain hope that they can get back together again. She knows it hurts me that she ditches me to have sex with him yet she still does it pretty indiscriminately and I don't know if I'm in the right to feel hurt about the situation or if I should accept that she loves who she loves.
Wow, that's really long. If any of you have the attention span to slog through all of that, I would appreciate the help immensely. I don't want to lose my best friend, but I don't know if we can stay friends like we are if she keeps doing this.