Third marriage and life as Countess Wesselényi
The Viennese court appreciated the couple's service. Emperor-King Ferdinand III thanked Wesselényi in a letter, while his wife, Maria Anna of Spain, wrote to Széchy and sent her a horse with expensive equipment. In 1647, Ferdinand bestowed on her the right to dispose of her estates in her will however she desired, lauding her bravery at Murány.
Széchy's third marriage, based on mutual sympathy, was happy and harmonius. The spouses both liked feasting, music, and receiving guests. Wesselényi gave Széchy the nicknames “Miczikém” (“my Miczi”, a diminutive of Mária) and “én asszonykám” (“my little wife”), praised her skills in managing their household, and complained how difficult it was to be far from his “beloved wife, [his] very dear nurse and keeper”. In Latin, he called her his “charissima, dulcissima” (“dearest, sweetest”) wife or “vitæ meæ comite”, (“companion of my life”). He seems to have considered her his equal and a partner in politics, making her one of the most influential Hungarian women of the time. She supervised the education of her step-sons, Ádám and László Wesselényi. In 1654, Ádám married one of Széchy's relatives, Borbála Homonnay, but he died in early 1656.
After many lengthy theological discussions with her husband, Széchy converted to Catholicism in 1645, adopting the name Anna in addition to Mária. Her conversion raised legal issues. The Protestant faction, for whom the apostasy of such a prominent noblewoman was a painful political loss, challenged the validity of her third marriage. Although Széchy had divorced her second husband, he was still alive. While Protestants could divorce and remarry, Catholics could only separate and not remarry as long as their first spouse lived. The Wesselényis turned to the church court of György Lippay, Archbishop of Esztergom (who supported them). Lippay asked the counsel of scholars at the universities of Nagyszombat (today Trnava, Slovakia) Graz, and Vienna, as well as John de Lugo. On 29 March 1645, he officially declared the marriage of Széchy and Wesselényi legal, arguing that her marriage to István Kun had been null and void. The next challenge was that Széchy and Wesselényi were related in the third degree, an impediment to their marriage in Catholic canon law. They received papal dispensation for this.
Over the years, the couple bought much of the Széchy estate from relatives. Every land they acquired became shared property and they both signed all documents pertaining to them. Because of the costs of official representation at political functions and their love of expensive clothing, jewellery, and entertainments, they were perpetually indebted. When loans could not cover their expenditure, Széchy mortgaged her jewellery. During the diet of 1659, she had to borrow silverware for a dinner as her own was mortgaged. They borrowed money from archpriests, aristocrats, friends, and charitable foundations, and goods from merchants. Acsády argues that their constant financial problems were the sign of a transitionary age, when land and agricultural produce could no longer cover a politically active family's expenses, but sufficient cash was not yet available either. Wesselényi rarely received his or his retinue's salary from the underfunded state treasury. He had to pay advances to his retinue to keep them in his employment, complaining that “great wealth makes [one] a beggar in public service”.
Wesselényi was often sick and Széchy nursed her diligently. She herself suffered from many illnesses and developed practical medical knowledge, making medications for herself and her husband when doctors were unavailable, evidenced by her letters ordering ingredients. She took care of her friends, household, and servants, sending wedding gifts and medicine. Just like her mother and her husband, she permitted her retinue and servants to choose their own denomination, but she made donations to Catholic monastic orders, especially the Franciscans.
In 1666, Wesselényi wrote his first will, naming Széchy as his sole heir. His only living son, László, brought a legal challenge, then fled to Poland. Later, it seems that the relationship between Széchy and László Wesselényi became cordial, as he entrusted his wife's care to her in his own will.
