She just accepts the fact that he cheated on her? I mean, i know he didn't, but she thought he did. It's true that she doesn't really have much self-esteem, but she should care enough about herself not to get back with a guy who (she believes) cheated on her without even questioning it.
shareI'm sure he explained it and they had a laugh about it later.
shareshe just saw him going on a date with a girl, a girl that lived in his building.
Im sure she probably asked him about the girl and he explained
You don't think the characters had an off-camera conversation where he clears some things up? Sheesh, how do you people not fall down more when you're trying to walk?
share1. Just after she saw him with the other girl in the restaurant and he didn't recognize her in front of the restroom doors and phones; he called her cellphone but she didn't talk to him saying only "are you a psycho?" and the movie made it clear that they never spoke again until the final act, as he mentioned she didn't answer his phone calls, he tried his father but her father pushed him away, he thought she was seeing Ralph, etc... I know it could still be argued they could have spoken off-screen but the movie production was definetely executed to make the audience think they didn't talk until the final act after that restaurant scene.
2. In the final act, we see their full conversation uninterrupted until she accepts him back, they passionately kiss, and seem to be back together again. In that conversation, there's no mention of the other girl incident and him not recognizing her.
So, I guess it's normal that people expect her to ask for an explanation or at least mention he was cheating on her before she accepts him back with open arms right? He said he loved her. The first thing she would think to say is something probably like "If you love me, what were you doing with that girl in the restaurant?" But she didn't. Doesn't feel normal at all.
Moreover, let's assume there were reasonable and sensible off-screen time intervals that they could speak and clear that misunderstanding before she accepts him back. It's still a creative mistake for a straightforwardly constructed movie to not include such an expected dialogue which is related to an important looking plot-point deliberately shown to the audience. We were shown her getting pretty upset after seeing him with another woman holding hands which would mean he cheated. In a simply constructed (not experimental/abstract/whatever) movie like this, if you are showing the audience a scene building a conflict between two main characters, you kinda have to adress and resolve it on-screen. It's against basic cinema story-telling rules which this movie definetely chose to follow.
I know it's not the most important thing in the world but the op is totally right about asking his/her question.