Legal Question in Landlord & Tenant Law in Washington

I hate to write this, but your friend has no rights to the property, including any right to remain there for any period of time. By virtue of the owner's death, assuming he died without a will (intestate) then his property passes to his heirs, which may include his wife, if he had one, and otherwise to his children, including your friend's boyfriend and his brother who are by operation of law, now the rightful owners.

So long as they don't do anything to her, she's fine. Without a lease agreement, the best they can do is try to bring an action to remove her from the property, since technically, she is now a squatter.

If I were her, I'd do my best to relocate as quickly as possible and not risk any legal entanglements that are needless. She ought to also speak with the brother and discuss what he wants her to do. Maybe he'd allow her to remain in the home to take care of it until he figures out what to do next.