I've had messy roommates too. Sometimes it helped to sit and talk about chore division and make up a schedule. Sometimes it's just a little adjusting on both sides - a bit messier than you'd like, more sterile than she would. But if you've moved in with a hardcore slob basically all you can control is your reaction. Decide what's really important to you (dishes washed, or counters wiped, or bathroom spotless, whatever) and resign yourself to the idea that you may just have to clean it yourself to avoid stress. Not fair, but is it worth more to be angry and resentful that it's not clean or to just clean it yourself?

The person who cares less in a relationship is the one with the most power, I once heard, and that's been my experience with slobs.

Hope it works out.