Her Guardian Cowboy by Danae Little

A struggling rancher, a single mom fleeing a life of danger, and the horseback riding accident that binds their lives together
Audrey will do anything to keep her son safe, including escaping the life of danger that awaits him. The small town in Wyoming seems like the perfect safe haven for them, and her son is eager to learn the ways of a cowboy.
Wesley spends his days struggling to keep his family ranch afloat and caring for his mom with Alzheimer’s. He starts offering horseback riding lesson to cover the extra expense of a miracle medicine that just may let him keep his mom.
A horseback riding accident propels them all on a journey filled with memory loss, new beginnings, and danger.