The first week and a half are August stayover (https://housing.utah.edu/apply-reserve/break-housing-stayover/) when the dorms are closed for maintenance and cleaning. But you just need to be in the state with evidence of that (spending on her debit/credit card is the usual way to prove it). So you would need to extend your vacation until move in (for freshmen usually the Thursday before classes start).
Remember that the following summer, she’ll want to either take classes (those are at in-state rates in the summer) or be there as an orientation adviser all the way up to the beginning of summer stay over (that’s what makes you eligible for summer housing). So really there’s only about 1-2 weeks of opportunity to go home in any case. Christmas is longer, but most people go back right after new year for a holiday (skiing is the obvious choice) and limit their time out of state to about 2-2.5 weeks.
Most people stay at fall and spring break (good for national park trips) and often for thanksgiving (last year was the BYU football game so no one wanted to leave, that’s not the case this year).