Quicksilver by Kyra Dune

Bound and determined to bring a criminal to justice, Quicksilver will chase him across dimensional space to do it. 

As a Guardian it’s Quicksilver's sworn duty to protect both realms from the threat Crimsonstar poses. But when she finds herself alone, wounded, and in desperate need of help, she is forced to break a taboo among her kind. In order to save herself from death, she has to drink the blood of a human. What she doesn’t count on, is what happens next.

Dustin's life is steady, if a little bland, until he stops to help a bloody, naked woman on the side of the road. He has no idea how his world will change with that one simple act.

With an undeniable attraction growing between them, Dustin and Quicksilver work to stop the criminal bent on killing them both. But will the unexpected appearance of a pyrokinetic from the second realm be a help, or a hindrance?