OK, nobody asked for this one. It's all my own idea, inspired by seeing the misuse of lose/loose just one too many times on a rainy day...you know, the kind of day when small things grate on you because there's nothing else to do! Dangerous stuff for us editor-types. (Yes, I know it is an incomplete sentence.)
Assuming the author in question didn't have a typo problem--in which case I send condolences, because I have one and it's a doozie--here are some definitions of lose and loose:
Lose: to misplace or bring to destruction, miss from one's possession or suffer deprivation. To suffer a loss. To fail to keep control. To fail to use. To fail to win, gain or obtain. To fail to catch with the senses of the mind. To miss one's way or bearings. To make oneself withdrawn from reality. To go astray. To draw away from or fail to keep in sight or in mind.
Wow! Who knew? But in sum total, "lose" is about loss. Lose=loss.
Loose: To work partly free. Not rigidly fastened or attached. To free from confinement. Not tight-fitting. Not brought together in a bundle. Not tightly drawn. Having a flexible and relaxed character.
Not one definition under "loose" has anything to do with loss. Loose=free.
So if you are worried that your heroine might "loose" the hero if she does such-and-such, remember that lose equals loss. You don't have to "loose" him unless you have him tied up.