It is rude to not pay back a friend.
Rose owes her friend money, and they are going to see a movie together soon.
Rose wants to maintain a good relationship with her friend.
Rose offers to pay for her friend's movie ticket to pay her back.
Rose hopes that her friend forgets about her owing money and makes her friend pay for her own ticket.
Rose's friend is grateful and feels like Rose is a trustworthy friend.
Rose's friend is annoyed that Rose didn't take the chance to pay her back and starts hanging out with her less.