My niece works for her agency. Yes, they would have shown the house if someone wasn't pre-qualified, especially a vacant property. One reason to pre-qualify prospective clients is to protect the homeowner. I certainly wouldn't want lookie-loos coming into my home without being prequalified but if the house is vacant, I wouldn't care.
I honestly think Beverly just let her guard down because these houses were right in her own backyard, her home community where she was well known. Scott is close knit. It was the last place she thought she'd come to any harm. IMO.
Thoughts and prayers to Beverly's family and to those in Scott and the Real Estate community.