How do I politely tell someone to leave my house?

Recently, an old friend of mine told me she was coming to my area with her boyfriend and wanted to know if I would like to see her. I agreed, thinking we’d only be meeting up for lunch. However, when she arrived at my house, she popped her belongings out of the car and came into my home. I did not know she intended on staying the night, but I just went along with it because I am not one to speak up. It is the third day of her staying with me; she has eaten all of my food, groans about her boredom, tells me all of her relationship problems, sleeps in my bed, and has one of the most psychopathic personalities I have ever witnessed.

I need her to get out of my house pronto. How do I politely tell her to go away and never come to my house again?