I know that many have claimed that there were girls named Alma after the Battle of Alma in the Crimean War. It seems that the Battle of Valmy would be something parents who were anti-monarchist might want to commemorate in the name of a daughter. The name was used in France itself in the early 20th century, thought it was rare. I can't find any statistics online on just when in the 19th century or before the first French Valmy was born, however. Perhaps Lumia could help with that.