One for Sorrow

I wouldn't go so far as to say it weakens her as a character, exactly. Plot-wise and relationship-wise Zuko is the person that Mai interacts with who is different from everyone else, and ultimately she winds up on the other side with that relationship being her path to it. She would probably be a far more admirable character and a role model if her journey was, like Zuko's, sparked off by seeing the suffering the Fire Nation caused and realizing how she'd been wrong in the past and had hurt people who loved her. But I don't think the fact that her change comes at the very end, so that we don't see what's going to come next for her, weakens her. Only because that begs the question of what's she's being weakened from. The girl who cared about her brother and doing the right thing to the point of either defying Azula or going behind the scenes to make sure Tom Tom was all right after they left or even seemed to think about it later is a different person who's maybe more admirable, but not necessarily stronger.