I feel that she's not even caring about the relationship itself, she is more intent on having a normal life. She doesn't want to get involved in any problems and doesn't want to start drama so she takes the easy way out. From having a 'normal' life from her popular mom and antisocial sister, she doesn't want to associate with any problems and thinks she is able to gain happiness from being normal and mediocre. That's also why she thought it was just easier to forgive him rather than start a drama when she knew about the cheating, I think it was already obvious from the start she doesn't like him romantically but only for outward looks of her standard of 'normal' she wants to maintain. She was crying not because he was cheating on her out of love, but it went out of line of the 'normalcy' that was supposed to stay, which she thinks cheating is not normal. But overall, especially her thought process, that's actually a pretty good storyline and actually a unique way of starting, I'm hoping to see the guy actually making attempts to change her ideologies, especially you see his standard of giving his all if he's serious about it and strives for true happiness. :)