What of Mei Terumi, the 5th Mizukage's marriage?
It's because she's not married yet in spite of her age, at least in Naruto Shippuden.
I don't know about her marital status in Boruto.

Edit:
For the downvoters, it's very common in many Asian cultures than an unmarried woman would be angry if somebody mention something related to marriage, especially when she's about 28 and up y.o. It's like if you ask "how much do you weigh?" to a woman.