She pretended to be house keeping and brought the brothers a new set of clean towels. Dean tried to tell her to leave, but after he opened the door Ruby forced her way in and urgently told the brothers to escape the motel room through the bathroom window, since they were demons surrounding them. She also gave them the cabin's address.
When Sam asked about her other vessel, Ruby told him that she had left her rotting, and suggested he sue her if he did not like her possessing the maid for "a hot minute".
Afterwards, Ruby returned to the brunette and presumably left this maid alive.