From the Oxford Dictionary of Saints: Elizabeth of Hungary

Elizabeth of Hungary (Elizabeth of Thuringia) (1207–31), queen.  Born at Pressburg, the daughter of King Andrew II of Hungary, she was brought up in Thuringia and in 1221 married its Landgrave, Louis IV.  Ardent, passionate, and handsome, she enjoyed a married life of extraordinary happiness, bore three children, and was generous to a fault, spending enormous sums on almsgiving, founding hospitals, and providing for helpless children, especially orphans.  But in 1227 Louis went on a Crusade under Frederick II; less than three months after, he died of the plague.  Elizabeth was first incredulous, then distraught almost to insanity; Louis' death was the turning-point in her life.

Her brother-in-law Henry drove her from the court; some advisers wished her to marry again but she refused; in 1228 she settled at Marburg under the spiritual direction of her confessor, Conrad of Marburg, whom she had known since 1225.  She became a Franciscan tertiary, expressing her ardour in love of poverty, the relief of the sick, the poor, and the elderly through building, and working in, a hospital close to her very modest house.  Conrad's direction seems to have been domineering, severe, and insensitive.  Elizabeth provided for others to educate her children.  Conrad made her dismiss her favourite ladies-in-waiting for whom he substituted two harsh companions, and would punish her with slaps in the face and blows with a rod.  She refused an offer to return to Hungary, preferring to live out her days in good-humoured and resilient exile.  She would occupy herself with menial tasks like spinning and carding, or cleaning the homes of the poor and fishing to help feed them. Her new regime lasted only two or three years: she died at the early age of twenty-four, her life shortened by her own austerities and the almost sadistic direction of one who had been a successful inquisitor of heretics.

She was canonized in 1235 by Gregory IX; in 1236 her relics were translated to the church of St. Elizabeth at Marburg where they remained as the object of enthusiastic popular pilgrimage until 1539, when they were removed to an unknown place by the Lutheran Philip of Hesse.  She is depicted on a screen at Tor Brian (Devon) of c.1500 holding a double crown, and in a 20th-century stained-glass window at Eversley (Hants).  Feast: November 17 (formerly 19).

You can read more about St. Elizabeth of Hungary in other references such as the Catholic Encyclopedia and Wikipedia.