My question involves landlord-tenant law in the State of: Washington

I live in Washington state. I moved out of my house without giving my roommate 30 days notice. My name was not on any lease agreement and I never even spoke to the landlord; I only moved in with the roommate without any sort of lease agreement. I never signed anything.

The house was on a month to month basis.

I was not told that I was required to give notice; I was merely told that it was a month to month agreement.

I never signed anything and was paying rent to the roommate, not to the landlord.

Now she is saying that I owe her for this full month's rent even though I moved out 3 days ago.

WashingtonLandlordTenant law says that you must give 20 days notice, but what if the agreement had nothing to do with the landlord?

Can she take legal action against me if I don't pay and will she likely prevail?