Name that book: 12th (ish) Irish/Scottish romance married heroine heals enemy in woods

Okay. So here goes. This is based in in the 12th to 15th century. The young heroine is a married to a miserable old, wealthy man. They live in a castle. I think her family is film of healers. He grandmother and or mom passed the knowledge on to her; quite possible that she is viewed as a witch. She goes into the forest to get away from her husband( I think he married her for money/status/heirs) and To find herbs. In the forest she find a wounded warrior; apparently, there is some bravehartish war going on between regular men and nobility. She and her husband are of the Nobel class and the wounded man is a regular man/warrior. She manages to get him into a cottage and she starts to use her healing training and helps him heal. She has to sneak away every night to feed and care for him in fear she is found out and the are both killed. They Begin to fall in love... I can't remember anything else and I can't find the book.

I read it within the last five years.