Mautner Markhof and Reininghaus had agreed on the Semmering as the sales border, until the 1970s from Styria only Gösser and Puntigam beers were delivered to the east. Nevertheless, there have been a number of lawsuits and disputes between the related families over the years. It began with the Reininghaus family claiming a share in the St. Marx Brewery and 50 years later it continued with the question of who was the real inventor of the artificial yeast. In 1909 Friedrich, a nephew of the Reininghaus brothers, claimed that he had been cheated of his inheritance by Adolf Ignaz and his uncle Johann Reininghaus and sued five members of the Mautner Markhof family, including the grandsons of Adolf Ignaz, Victor and Georg II for a supplementary compensation of one and a half million crowns. During this trial, the two cousins countered that there had already been a payment of one million guilders in 1889. Irregularities in the inheritance payments could not be proven and so the Supreme Court finally dismissed Friedrich von Reininghaus’s complaints, which had cost him a fortune due to the length of the proceedings.
In 1901, after her husband´s death, Therese had to take over the brewery. Johann Peter had made her the sole heir, although she had born ten children (like her parents), including three sons. Their son Gustav, who was to be heir, had died at the age of 32, his only daughter Emilie (Emmy) married Georg II. Mautner Markhof in 1900. Although she had never intervened operationally in the business, Therese ensured the existence of this large business by converting it into a stock corporation and choosing the right men for the management (including her son-in-law). When the Second World War broke out, the Reininghaus family was forced to emigrate. After their return from exile, they transferred the beer production to Puntigam. In spite of having moved production, the family held onto the mostly fallow fields. The fate of the brewery was determined by its descendants until the 1980s.
Therese herself was also very socially active. She founded a foundation for widows and orphans in Graz, committed to girls’ schools and the admission of women to university studies, participated in the foundation of the Graz Tramway Society, in the electricity plant in Lebring and in the construction of the Grazer Schlossberg hill funicular. She lived in the Styrian town of Thal, where she and her husband had bought and renovated the Hardt Castle.