That style of glasses are often seen as the schoolgirl look but I can think of other reasons why she might wear them at times. If they are photosensitive she probably wears them as her sunglasses. It would make sense to wear them outdoors or when leaving the house. If they are prescription it's cheaper to have photosensitive prescription glasses than one pair of clear glasses and another pair of prescription sunglasses.
Also if she's nervous about facing strangers she might be tempted to keep wearing them as a way to hide a little bit. That could fit the situation at Passages where she was clearly uncomfortable. She might have just left them on after she walked indoors once she saw all the people who made her feel outclassed.
I wear contact lenses now but when I had photosensitive glasses I didn't really need them at conversation distance. I only took them off, though, if I was sure I wouldn't lose them and if I was comfortable with the people around me. I guess an observer would have had trouble telling my glasses wearing patterns, too.