If i were you, just to gauge her behavior, i would:
Stop doing her any favors whatsoever. Do not clean up her dishes, and when given a chance, ask her to get hers out of the way
Start ignoring her, or better yet just lose yourself in work
If she suddenly becomes interested in you again, she either invented this new guy to get you interested in her, or is a person you should avoid at all costs. The first is harmless, the second is a huge warning sign.
If she does not react at all to your sudden disinterest (after say, weeks), then she's probably a well balanced person and possibly a good friend to have. She's probably just busy, or focusing on that guy, being faithful to the thought of him etc. Be prepared for continued coldness, but at least know it's not something you can do something about.
Then of course, maybe you came on strong and she needed space. If she shows relaxed attention to you after you not paying her any special attention, that's probably it.
Ignore her -> her frantic attention towards you = no good, be prepared to leave
Ignore her -> no result = not your problem, she's just busy
Ignore her -> slow, relaxed return to interaction with you = she needed space, you might have come on too strong with friendliness