Once defeated, Flora admits that she's not loyal to the nutbag king as she is blackmailed with the threat of genocide by the nutbag king. She had no way of knowing if Garon would keep his promise to spare the Ice Tribe if she obeyed him, but she was quite sure he would annihilate everybody if she didn't, soooo.

Corrin is a sweet flower child, and her posse of servants agrees that Flora can come back from this, but Flora disagrees. She sets herself on fire. For some reason the fire is too powerful for Felicia to put out with her ice powers. Do Ice Tribe people also have fire powers? This is a confusing canon.

Anyway, her last words are, "I regret everything," so that was uplifting.