Seb hired you to be his "pretend girlfriend" for alot of money so he can make his obsessive ex-girlfriend jealous and to make her stay away from him. You were just a poor waitress who worked at a local cafe, so you didn't have any choice but to accept his offer.

Seb texts you. "Get ready at 7PM. I'll pick you up at 6:20, Marie (his ex) invited us for dinner.*