Not sure if anyone has read this trilogy by Pamela Kauffman. It's set at the end of the 12th century. It picks up right as Henry II is murdered by his son Richard I (Richard the Lionhearted). Mary Alix's castle is sacked by a greedy Duke who wants her land and her parents won't marry her to the Duke. On his dying breath, Alix is instructed by her father to travel to Henry II to ask for his intervention....disguised as Alexander, a boy.
"Alexander's" travels upon learning of Henry's death to Richard for aid brings her to the Crusades in Shield of Three Lions; to Richard's imprisonment, later freedom, and skirmishes with King Phillip of France in The Banners of Gold, and through King John's tyrannical reign upon Richard's death, to the Magna Carta in The Prince of Poison.
Alix proves to be an unusually strong, lucky, and plucky heroine for the middle ages. She finds education, love, romance, fulfillment, sadness, loss of unspeakable proportions and survives it all.
If folks here can bear to read brogue and "soothly" language, and after 5 chapters you won't notice anymore, I recommend it.