Somewhere in France by Jennifer Robson

Lady Elizabeth "Lilly" Ashford is a member of the British aristocracy as World War I breaks out. She wants to get an education and see the world but her parents want her to get married and have children. So she takes off for London and gets a job painting buses. She's long had a crush on her brother Edward's best friend, Robbie, a surgeon from humble beginnings. Robbie encourages her to pursue her dreams...which leads her to Somewhere in France, where she becomes an ambulance driver, ferrying injured soldiers to the medical base where Robbie is working as a surgeon. When Robbie realizes what he has set in motion--and the danger his suggestion has put Lilly in, he is beside himself. He tries to convince her to go back to England but she loves her job and helping with the war effort, so she refuses to leave. It's a good story about life at the front from the perspective of the medical teams and of course there's a love story. Truthfully, I thought the love story was veering too much into the "heaving bosoms" territory of a romance novel, but I liked the basic story of how the war impacted Lilly, Robbie, and Edward.

I just discovered that there is a sort of sequel to this book featuring Edward and Lilly's friend Charlotte, who took her in when she ran away to London. I will have to find it at the library and see what happens next.