Yes, wild yeast and spontaneous fermentation are things in the beer and wine world. Yes her beer is possible. Also it will be possibly very bad. Or fine.
You could totally make a sourdough by rubbing your butt cheeks in the starter every day and I don’t think your friends would notice.
Its funny, because 200 years ago there were no commercial good products. To make beer you basically had to let it sit out for a couple days until enough wild yeast colonized your food. This is also true of kimchi, saurkraut and a bunch of other ancient foods.