And this is the canon-compliant alternate ending. Well, sort of canon compliant. If you use your imagination.
She touched Zuko's face, and he shivered. At fourteen, she'd been dangerous, but cute, sweet, laughter personified.
Now she was cold, dark, obviously deadly…and she was part of Sokka's plot.
How had this happened? Sokka turned against him, Ty Lee turned against him…
"The age of benders is coming to an end, Zuko," she murmured. "We will not be relegated to the shadows anymore. Our voices will be heard."
An explosion rang out, deafening them all. Shouts, fire blasts, clanging metal…
Zuko was dragged back, and saw Sokka and Ty Lee dragged forward in chains.
"Kill them," Mai commanded coldly.