What the Cui Family did was extremely outrageous, so much so that even some of their own members found it hard to swallow.
For the Xiao Family, all they wanted was the bloodline of the Cui Family, so as long as they dispatched anyone from their direct bloodline for marriage, it didn't matter whether they were beautiful or ugly.
Status and beauty notwithstanding, the Cui Family clearly didn't want one of their legitimate daughters marrying into the Xiao Family to live as widows; that's why they'd chosen Cui Yueling to be married off.
This way, they could weed out the unworthy while ensuring the complete severance of the main bloodline embodied by Judge Cui.
This issue being a sensitive one, neither the Cui nor the Xiao exposed their chosen marriage partners prematurely. They saved the revelation for the actual day of marriage, aiming for an unexpected, sweeping resolution.