a.) chuck a ceramic bowl at her door
b.) put her dirty dishes in her room (i've had a roommate do this to me)
c.) leave all her dishes in the sink FOREVER (cuz that's how long they'll be there if you don't do them)
d.) unload (or load) the dishes REALLY loudly early in the morning when she's asleep.
e.) put a big neon sign above the sink that says CLEAN UP YOUR CRAP!
I can only admit to actually having done d. I've had enough self control to avoid the rest. But oh, have I been tempted.