The family and social pressure, especially in Utah, is enormous, but she also would have been conditioned since earliest childhood that her full eternal salvation and exaltation requires her to marry in the temple, preferably to a returned missionary. Lots of Mormon girls will flirt to convert, but the vast majority will eventually insist on full conversion and temple marriage.
Here's a quote from October 2023 by Russel M. Nelson, the recently deceased President, Prophet, Seer and Revelator. He is addressing the entire church at general conference (twice a year, instead of church, the Utah authorities give talks that are broadcast worldwide in church and over tv/cable).
https://www.churchofjesuschrist.org/study/general-conference/2023/10/51nelson?lang=eng
Without a temple marriage, you are no longer married in Heaven. You don't get your own worlds to create and rule as a god/goddess without a temple marriage. Both husband and wife have to have active temple recommendations and maintain them. That requires not just membership, but full compliance with all church rules, serving in non-paid church callings and paying 10% tithing among other things.
It's enough pressure to break up MANY otherwise healthy relationships. If the reported info about a Mormon ex is true, it's a likely factor.