I think she just can't say the fact that she misses the guy so much, so she say bad things about him to help her get over their previous relationship. And she wants the guy to apologize, which could mean: "i want you back" or "let's just finish this and be friends". She wants it to be too formal, it could be the first reason. In the end, the lines about the 7 things she like about him pop out, which made the message of the song really obvious. It's for nick!