she's blackmailing you? super easy to get rid of that problem, dude
carry a recording device in your pocket, get her to say it again in casual conversation "i really think i should tell mom & dad about you drinking" or something like that. then just have your parents listen to the recordings and boom, you're done. not petty at all because it's for her own good.
and what kind of blackmail is that anyways lol, ain't nothing wrong with research