Oorah!

Oorah! The Adventures of a Brave Girl is the story of an American ten-year-old tomboy. Although her name is Samantha, she prefers to be called Sam in honor of her father's first name. Her greatest desire is to become as brave as her dad, a United States Marine who died in battle during the Vietnam War.
Although Sam's mother, Priscilla, is also American, she was born and raised in Surrey, England. Priscilla decides to send Sam to England for the summer where the youngster will be greeted by her grandmother, the Duchess of Surrey. Priscilla hopes the duchess will turn her little ruffian into a proper lady. Will it work? Even Priscilla has her doubts.
As soon as Sam arrives, she meets an English boy, Oliver, who is a year older than she. Together they have one riotous adventure after the other-riding across the English hillsides on horseback with their trusted Great Dane at their side.
How will a rough-and-tumble ten-year-old girl deal with lordly British aristocrats? How will she battle a ghostly knight come to life? How will she capture the one animal the English could never land: The Beast? And what mind-boggling discovery will make her an international celebrity?