Dirty and unhygienic roommate that I just can't reason with!

I have been dealing with a dirty roommate for almost two years now. The most common complaint is her leaving dirty dishes in the sink for a long time. She left on a week-long holiday without washing her dishes. I had had enough, and so I put all the dishes in a box and put it outside her door. I came back from a weekend trip, and those dishes are still unwashed. We had a big argument regarding it, and her response to me is, 'Are you my landlord?' There's no way I can reason with her, and all I want is just a slightly cleaner kitchen to cook in. Being able to use the sink without it being filled with dirty dishes and food. This affects me mentally, but I cannot afford to move out. It also feels slightly unfair when the person being inconsiderate cannot be held responsible. I just don't know what to do!