For the full text see here. A girl has had an argument with her boyfriend. On the way home she thinks that maybe she should have apologised. She's now changing the password on her room door.
While absentmindedly messing with the characters, the phrase "It's my fault. Sorry." was lined up. Even though it's no use saying such a thing at this late stage, I'm an idiot, aren't I? However, tomorrow I'll spend time saying these words.
I don't fully understand this passage. What does こんなこと refer to here? Is it the phrase 悪かった、ごめんなさい or is it あたしもばかね. i.e. Is she saying that there's not point in calling herself an idiot, or is she saying there's no point in saying it was her fault?
Presumably この言葉 refers to 悪かった、ごめんなさい? I'm not confident that I'm putting all this together correctly.