wearing sunglasses indoors

I’ve been going to the bookstore cafe more lately since I’m studying for a test (can’t study at home b/c of comfy distractions such as sleeping and snacking).

Today at the bookstore cafe, I saw this one woman wearing dark sunglasses while reading a book. This is not the first time I’ve seen her do this. She’s done this after dusk before too.

So why would anyone want to wear sunglasses indoors? Is it a fashion statement? I can understand if you’re playing poker and don’t want to give off tells. Does she have something to hide? Or she has a health condition or maybe wearing sunglasses indoors makes it easier for her to read? Pink eye everytime she’s at the bookstore cafe? It’s interesting b/c everytime I see her, she’s by herself and sometimes she’ll have it off and sometimes she won’t.