NGL, this would be a dealbreaker for me too, dude.
My sister in law is like this, and me and my father can get quite worked up over it. She comes over for dinner and leaves, you are guaranteed to have at least 2 half glasses of water, 1 or 2 wine glasses (one red, one white or whatever), a half-drunk cup of coffee, an open but unfinished can of coke,, etc. In the weirdest places, too. She'll take them along to drink while putting on her shoes then leave it unfinished in the hallway, another on the window sill, a third somewhere next to the computer,....
I've literally once recovered a half cup of tea from the toilet!
What irks me most though is that she STILL does it with "rare" or "special" things. If I have a small bottle of some fancy shmancy whiskey or something, with just enough to give everyone half a sip, than I'm not exactly thrilled if SOMEONE is gonna leave half her glass of it. I've actually had a discussion about this after I pretty much wasted $10 worth of something on her, and now in this sort of situations she'll just drink from my brother's glass/cup/mug/whatever. They don't mind sharing, and at least my brother FINISHES his damn drinks.