Turner: World Change

Born on Earth of human parents, because of an ancient magical spell, Juri Turner transforms into a dragon in order to help fight and defeat the Artesio, aliens who invaded and subjugated Earth two decades ago. She does this by opening a door to another dimension and getting help from the magical dragons and humans who originally cast the spell. It was their way of repaying the humans of Earth for having helped them in the past.
Then Juri learns that in addition to saving Earth she was also born to save Mur from total annihilation.
However, as she learns, being born to accomplish a task doesn't necessarily mean it'll be easy. First, she will have to escape dying on the job, and if she does then she has to contend with being forced into marriage...
How will she handle being betrothed to a dragon?
Pray for Mur, pray for Earth, but especially pray for Juri, for without her, both worlds are doomed.