Coffee B.
Have her set up a good video monitoring system from Costco and record. She may very well find that although she thought it was impossible someone was getting in that it's exactly what's happening, especially when real estate may be involved.
Another possibility is that people process information at differing levels of consciousness. We all have had the experience of getting in a car, and driving somewhere only to all of a sudden 'come to' realizing we had 'spaced out' during most or all of the trip. Sometimes I put things places, or pull something out and put it someplace strange not even processing what I'm doing only to discover it later.
There's a logical explanation if she's willing to put in the effort to find out what's up. She may see in her own recordings that SHE put the dress there (or someone else got in)...who knows.
People often default to the 'easy' explanations involving the paranormal.