Highland Rebel by Sally Watson

Bonnie Prince Charlie's attempt to capture the throne of England was a time of high excitement for Lauren Cameron, her brother, and her cousins. It was a serious time, too in 1745 Scotland, with dreadful happenings and fierce battles. And Lauren, kept at home with Aunt Elspeth, longed to be out fighting the British. Donning kilts, she would ride over the hills with her cousin Murdoch and faithful Angus, looking for British soldiers. While masquerading as a boy, she was captured and held prisoner by the Earl of Loudon, head of the Campbell clan, arch foe of all Camerons. Still refusing to admit her identity, Lauren finally escapes, and rejoins her family and those loyal to the Prince into exile in France.