I'd be tempted to encourage her into some counselling. Many girls grieve when they reach menarche, and do not deal at all well with their periods. (Sticks hand up.) There may be a rebellious denial in what she's doing. Lack of personal hygiene in that age bracket when it is to that extent can also be indicative of greater mental health issues.

I think in the meantime expecting her to do her own washing is perfectly reasonable and doesn't have to be done in a punitive way. Just, "It's really unpleasant for me to be cleaning up after you like that, so you'll have to wash your own clothes when you've got your period, I'm afraid."