When Lucy is harassed by the drunk guy and Ben comes to her rescue, they all bolt out of the bar and Mimi grabs all the money they'd made, cupping it in two big handfuls. When we see Mimi running out, she only has a small bundle of money in one hand.
When Kit is revealing the worst and best thing that ever happened to her, she is eating strawberries. She take a bite of the strawberry and dips it into the whip. Then when she goes to bite the strawberry again it is a new strawberry with no whip on it.
Kit is driving from the oceanside motel to see her boyfriend at UCLA when Mimi asks why they are on Melrose instead of going sightseeing. But UCLA is between the ocean and Melrose. (There's no indication they are lost.)
When Lucy is on the phone to her dad and everyone is loading up the car outside the second hotel, Mimi is putting her stuff in the trunk of the car. You see Mimi look over at someone, shrug her shoulders and say, "What?" The directors were telling her that she was in Lucy's shot.
After Lucy finds out she is a mistake, she and Ben walk out of the bathroom to go talk to Mimi and Kit. In that scene, Mimi's shirt is lifted a little, revealing the white, fake pregnant stomach she was wearing.