I read a really moving book years ago called "Sorrow Mountain: The Journey of a Tibetan Warrior Nun".
I don't know if it's the one you're looking for, here's a synopsis:
Ani Pachen was born in 1933, the daughter of a powerful local chieftain in the great, wild expanses of eastern Tibet. Soon after her twenty-first birthday, as the Chinese invasion thundered through her countryside, Pachen's father died, leaving her in charge of her family and the freedom fighters he commanded. Overnight, she became one of the few female leaders of the resistance movement until she, her family, and hundreds of her kinsmen and neighbors were finally captured and imprisoned. For more than twenty years she endured relentless torture, enforced labor, and near starvation in Chinese work camps. But Pachen's legacy of grit and defiance, as well as her single-minded devotion to the Buddha's teachings, helped her survive, and, ultimately, to escape to India, where she ordained as a nun and met His Holiness the Dalai Lama