SOLVED - HR with a camp follower/nurse h

The book takes place during the Napoleon wars.  The h is a British  camp follower, or maybe daughter of a soldier or officer. She helps out in the medical tent nursing the wounded. There is a conflict between the H who is a soldier and an OM who wants to marry the h. The camp has to break up and retreat, and the H and h are left in the rear with the wounded.  As they get to each town or village after the rest of the army has been through, they discover the OM has been spreading lies about them so no one will help them. They are even held prisoner in one place and the h is forced to help deliver a baby. This is where they discover the lies that have been spread about them.  

This is where I get fuzzy. I think this is the same book where they end up in a village populated by descendants of the lost Roman Ninth Legion. This part may be a different book and I'm mixing them up.