Yes, if the diploma is a post-secondary diploma or certificate in hotel or restaurant management and she has three years of experience in hotel or restaurant management. Either a degree in the field alone or the diploma-plus-experience combination satisfies the entry; industry experience without a qualifying diploma does not.
Two ways in, and both are specific
The hotel manager entry is one of the few on the USMCA list that accepts a diploma rather than a degree, but it attaches a condition: three years of experience in hotel or restaurant management. Both halves must be shown. The diploma must be in the field, so a Harrison Hot Springs applicant with a two-year hospitality management program qualifies on the education side, while someone with a business administration diploma does not, regardless of experience.
The experience must be management, which means supervising departments, staff and budgets rather than working in the industry generally. The position offered must itself be hotel management; a general manager's title attached to a role that is mostly sales or events would be questioned. The applicant must be a Canadian or Mexican citizen, must hold no ownership or control of the U.S.
lodge, and must intend to remain temporarily. A Canadian may apply at a port of entry or through an employer's Form I-129 petition, and no visa stamp is issued either way.