This morning when I dropped S17 off at work, both STBX's car and OM/Boss's car were there. S17 said "what's she doing here? she's always here when she doesn't need to be and is doing nothing". I almost bit my tongue off. STBX was there on her day off for the same reason she has always been at that restaurant all the time - to be near her Boss.
Now that they are openly involved and live in the same apartment building, I would think they would spend their time together away from the restaurant. I think she's addicted to the restaurant and it's culture, just as much as she is addicted to him.