Tenant wants to move out

[Joshua M. Jones]

So I have a tenant who has been a problem tenant. Their year long lease expired in October and now they only paid part of rent for December and nothing for January. I just received a text that she will pay what she owes and be out by the end of the month. I live in Washington state. I believe she is required to give me 20 days notice and then she’ll be into the next month so won’t she owe for the following month as well? Any help would be much appreciated.