Ash and Feather: Flame and Sparrow Duology, Book 2 by S.M. Gaither
How can the female leads in these romance fantasies be so stupid? They totally forget their goal of saving the world and fall in lust with some random bad guy. Here the elf leader learns to fly, and uses that as a chance to have an affair. She later finds her sister, who is aligned with the bad side. Why is that side bad? Well, it just is. She falls for another guy. The sister comes around and they eventually do what they wanted to do. The writing and story are bad, but better than the typical romance fantasy.
