@florencedc
I will do some more searching (live in Rochester), but one option is to contact Mayo Clinic's free Concierge Services? Usually provide information for patients, but may be able to suggest temporary housing for volunteers.

Concierge services
https://www.mayoclinic.org/patient-visitor-guide/minnesota/concierge-services
By phone 7 a.m. to 6 p.m., Monday-Friday: 507-538-8438
Email: concierge@mayo.edu

There is a company that owns some smaller apartments buildings that do short term leases, I see the Parker has room available in June. Nothing fancy. I do not know anything about these apartments, but assume better price the larger units in Rochester. https://www.residentproperties.us/

Mayo has an on-line classified for employees that I can not assess (not an employee), there may be ads on there. Does she have a contact with a Mayo Employee who can check the Mayo classifieds?