The Descendant by Melissa Riddell
She wants her world back; he wants her heart.
Tilly Morgan and her four-legged companion, Kodiak, are trying to survive an alien arrival. Two years ago, the unearthly visitors unleashed devastation–a world-wide EMP followed by a deadly virus that has wiped out most of humanity.
Traversing the lonely landscape, she runs into an alien on patrol with one order: eradicate all human life. A charismatic, dark-haired stranger named Jareth comes to her aid, and she reluctantly allows him to join her quest to find her sister.
As her group travels the desolate world and inches closer to her goal, she’s forced to examine her unwanted feelings for Jareth and come to terms with her heart, even if the truth threatens to destroy her and everything she’s come to believe.