She was married according to the Roman Catholic rite into the Styrian noble family of Eggenberg on 23 October 1639 in Regensburg[1] to Prince Johann Anton I von Eggenberg, Duke of Krumau, who subsequently received the opportunity to acquire the shire of Gorizia and Gradisca along the Adriatic coast two years later from his boyhood friend, Emperor Ferdinand III.
[2] She demonstrated a strong character and conviction by holding on firmly to her family's Protestant faith[3] in spite of her marriage to the son of Hans Ulrich von Eggenberg, chief minister of Emperor Ferdinand II, who had prosecuted the Counter-Reformation in the Habsburg hereditary lands as well as the Thirty Years' War.
Upon the early death of her husband in 1649 Anna Maria, together with her father and Wolf von Stubenberg held the guardianship of both underage sons, agreeing to remain in Habsburg hereditary lands and to raise them in the Catholic tradition, as well as administration of the Eggenberg possessions.
Anna Maria further demonstrated her mothering instincts by going personally to the emperor himself to request that her daughter be compensated with an equivalent sum as a dowry.
[7] Upon a visit to the town of Ödenburg (Hungarian: Sopron) in Hungary in 1670, she found the religious tolerance more open than in the staunchly Catholic Duchy of Styria and relocated her court in 1674 there to a small city palace, compared with the castle in Krumau or the Palais Herberstein, a city palace in Graz.