I asked a friend to explain this to me
she said:
The brown haired ugly guy is her boyfriend (or friendzoned guy) but then the blonde ugly guy pulls her into the world of modeling and fame and she becomes infatuated by him. Then the brown haired ugly guy comes to that party and the blonde guy offers him money to be his model. And when he is leaving Rita gazes at him and realizes he's the one she loves and decides to break free from that life only to find the Big Lips posing naked for the blonde ugly guy. Disappointed she runs off with her perfect titties bouncing and bouncing