Kara Zor-El had quite the journey in Supergirl, but she did NOT marry in the show. In the episode, Mr and Mrs Mxyzptlk, Mxyzptlk puts Kara in a wedding dress and proposes to her within seconds of meeting her. It was also during this time that Kara and Mon-El were starting to develop feelings for each other and Mxy saw Mon as a “threat.”
Mxy thinks Kara is playing “hard to get” when she says she won’t marry him. By the end of the series, Kara is unmarried, though her adoptive sister, Alex, marries James Olson’s sister, Kelly.
It might’ve been due to the heartache that befell Kara when Mon-El returned and was married to Imra Ardeen/ Saturn Girl that it turned her off marriage. There might’ve been a chance for Kara and Mon-El to get back together at the end of the series, but the idea never manifested. However, they remained friendly.
The Loss Of Mon-El
Losing Mon-El was devastating for Kara, and her friends could see how much his “loss” had on her. It was clear during the Season 3 premiere that Kara and Mon-El might have had a chance to marry.
Finally, the way the show’s ending was handled, it didn’t need Kara to be married to be happy. All that was required was for her to identify as herself, Kara Zor-El/Kara Danvers and as Supergirl without hiding her identity. When it comes to any series with couples, the lead character is always expected to be married off. However, it’s not always necessary for the protagonist to have a happy ending to their arc.
