Elisabeth did marry Otto von Windisch-Grätz. But they eventually separated and divorced after having four children and many affairs (for both sides). Then she married one of her lovers. She had quite an agitated life
being nicknamed 'the Red ArchDuchess'...
Elisabeth (Erzsi) met her second husband, Leopold Petznek, at Social Democratic Party (which she joined in 1921). Erzsi and Otto were already separate in 1918 (after a troubled marriage and both partners open in having mutual affairs). But after a long process, especially with regard to custody of the 4 children, it only became official in 1924. In 1929 Erzsi bought a villa in Vienna, where she lived with Petznek for the next 20 years. Petznek was married (with one so), his wife died in a psychiatric hospital in Mauer-Ohling in 1935.
Erzsi formally divorced Prince Otto in early 1948, and on 4 May 1948 she and Leopold married in a registry office in Vienna.
Petznek died in July 1956 from a heart attack. Elisabeth, who was wheelchair-bound much of the time due to gout, bred German Shepherds, but became reclusive until her death in 1963.
Erzsi reminds me a bit of Willy of Wales. She was also a spoilt brat and her grandfather allowed her everything mainly, because he felt quilty for what she had to (supposedly) endure in childhood. Erzsi had neither a good relationship with her mother - whose second marriage to a mere Count she doomed beneath her (mind you, when even FJ himself was happy for Stephanie finding someone again) - nor with her children.
During the 1920ies and 30ies, when they weren't able to get work and were basically starving she didn't lift a finger to help them. Not surprisingly the most harsh biography of Erzsi comes from her daughter-in-law Ghislaine d'Arschot.
When her mother wanted to publish her memories, Erzsi had them banned.
She and her husband already lived separated long before the fall of the monarchy, they just couldn't make it officially as long as the Empire prevailed. There's even a story of Erzsi coming home once and finding her husband and another woman in bed, firing a pistol at both of them. Luckily nothing happened.
When she died she had become totally estranged from her wider family and children, leaving the Gemeinde Wien her fortune, while her surviving children only got the legal portion.
I probably shouldn't say this, but I'm actually happy that we had male preference succession at that time or else Erzsi would've been Empress.