My question involves a roommate in the State of: Washington

I moved out of my apartment this past week. The apartment was on a month-to-month basis, and I never signed any sort of agreement. My former roommate is claiming that because I failed to give her 30 days notice (which I never agreed to give, not even verbally), I owe her this full month's rent. Am I required to pay her anything? Can she take any legal action against me if I don't?