Jedi you want to know the truth? You are her fuck buddy. And you almost blew it.
With sex and relationshops you often have to read between the lines. Women dont always want to tell you they only see you as a friend or fuckbuddy
She has a boyfriend, most likely the guy she is living with
The trick is not to get attached to her emotionally. You made the mistake of confronting her rather then just going with the flow. When a woman is giving you no strings sex and you are not meeting her friends, just enjoy the sex while it lasts