What was the point of living if she was to lose everyone she had held dearly in her life? No magi were able to survive before her and she would be no different from them. She was no exception. It would have been a different story if her magic returned.
Even her dark magic would be enough for Iris, didn't Killian say that her dark magic was only acting according to her emotion or if her life was under threat?
Alas, in the end, she also lost her dark magic. So what made Queen Asheera think that she would be strong enough to withstand the changing ritual? Did the High Queen expect that she could force Iris's magic to resurface like this?
Iris didn't want to be a queen of some court she didn't care about. She was just a poor girl who was struggling to make ends meet for her family. Why did things turn out like this anyway?