Taking Angels, book 1 of The Angel Crusades
by CS Yelle
Britt Anderson went along with everything the doctors said for four years, but she was still dying at eighteen. The cancer left her without any control except for how she would leave this world.
When Allister finds Britt's broken body he does the unthinkable for his kind, he brings her back. Now they must keep her a secret from the Eternals or both be destroyed.