She could be actually having mental / emotional / high problems, or something could actually be going on. I tend to assess unusual behavior based on other clues about them, and a telling one in this case might be her way of being and the way she laughed, which I didn’t get to see/hear. I imagine (since that’s all I can do) that if I could hear the laugh, I would at least be able to take a guess about her state – did she sound “all there”, disturbed, drunk, nervous, bratty, etc?
I agree it could be a dare or joke or something. Maybe the woman she was with (mom?) had made some statement and the daughter was off to prove it wrong?
It could also be that she was deep in her own head due to drugs or stress or fatigue or grief and/or self-spiraling, and had something in mind but then shifted modes from one where she would ask to one where she would laugh and run away.
If you had said she were more interestingly dressed and/or there were something more interesting about the situation, I might think it was a social experiment or art attack or something, but it was so bland and substanceless that it doesn’t sound like it. Maybe she has friends who do things like that and was spacing out and thought it made sense but it didn’t translate.
She didn’t really give you much at all to go on, and we have even less via text. However I think it is interesting that a trivial non-communication can be so unsettling. That’s also pretty interesting.
It suggests to me that the place where you live and/or your own routine in pretty homogenous and predictable, when something minor and unexplained gets so much attention. Compared to, say, an international city where there is a wide variety of people including frequent foreigners who don’t speak the language and may try but get embarrassed and fail (another possibility), for example.
If she was a customer, I wonder what you expect customer service would/could do about it?