Fall by Claire Kent

As a pilot and a smuggler, Lenna has spent her life flying under the radar in Coalition space–taking care of herself, not relying on anyone. She’s always liked it that way.

But now she’s stranded without any resources on a stone-age planet, and the only way to survive is to hook up with a bunch of cavemen. She’ll do whatever she needs to do in order to survive in their world–even if it means letting one of them take her as a mate.
She doesn’t expect to like it. Or like him. Or lose her heart in the process.