As the daughter of Humphrey de Bohun and through her mother, descended from Llywelyn the Great, Mary and her older sister, Eleanor, inherited substantial wealth and power.
Eleanor was married to Thomas of Woodstock (youngest child of Edward III) and Thomas had no intentions of sharing his wife’s money- so he pressured Mary into becoming a nun. However, Thomas’ older brother John abducted her from the convent and had her marry his son- the future Henry IV. Needless to say, this caused a few problems between the brothers.
Because Mary was only 12 when she married Henry, her father-in-law (yeah, the one that abducted her) arranged for the marriage to remain unconsummated until she was 16 (how kind of him.) BUT, the couple did not listen to him and Mary became pregnant at fourteen.
She went on to give birth to 7 children- 6 living to adulthood. She died giving birth to her last child, daughter Philippa of England. Mary was never crowned a queen because her husband did not become King until after her death.