Her rushing to jump into a relationship with the mc after her breakup with Chad, and her pushing the mc to take charge within the DIKs (at least to start organizing the Halloween party) does give credence to the idea that she likes to be linked to the important people in the college. First Chad, who obviously wasn't interested, and now MC (even if he's not interested).
Added to that, if you look around the college, who the fuck else is a girl gonna hitch up with? The good ones are taken (Magnar for one) and most of the other dudes are pretty hopeless.
What's also interesting about her wanting to be with the mc, if he's playing the field (of course he's playing the field), Sage kinda knows it, and for a whle she doesn't care, but once they become a couple, she's gonna care about his philandering, so at some point they are gonna have to have that talk:
Sage: "OK Fuckface, it's now time for you to stop fucking every other girl on campus."
mc: "Awww."