Her Invisible Soldier by Grace Risata

After the death of his best friend in an ambush, Dixon Wade returns from the military a broken man. Bitter, angry at the world, and suffering from Post Traumatic Stress Disorder, he feels invisible and forgotten by everyone around him. Everything changes when he meets her.

Fiercely stubborn and independent, Alyce is accustomed to doing what she wants, when she wants. Forced to volunteer at a charity in order to keep her job, she burns through every opportunity in town until stumbling upon a place that serves veterans.
Once these two volatile personalities collide, a battle of wills ensues. Never one to back down when faced with a challenge, Alyce comes up with some very interesting ideas to get her soldier back on the road to recovery.

Just as things begin to heat up for this unlikely pair, mistakes are made that could derail their entire relationship. Will Alyce be able to put the past aside and find a future with her invisible soldier?