went to my periodontist yesterday for a 55 minute teeth cleaning, and my wife works one day a week assisting our dentist which is how she already got the first shot two weeks ago !!
However with all the cleaning they do between patients, gowns, masks, sanitizer, gloves, maybe she got it from another patient ? Perhaps checking the temperature as one walks in isn't enough ? And is your DIL absolutely certain she got it at the dentist ? Did they close later on when a member of the staff came down with it ? Was your DIL anywhere else in the previous ten days ? I am just saying that all this contact tracing going on - its far from an exact science, just a way to quarantine EVERYONE in contact.