Luckily, she doesn't actually need a window like women do. She has so many regular clients that she could do it at home. (Although I don't think she wants to do it that way.) So she just needs a location, because she has plenty of clients.
And in addition to what you said, that you don't know her well enough to just leave without saying anything. So far, she's kept all her regular admirers in the dark. There's undoubtedly a reason for it. However, there are endless ways to still let someone know. Even if it were just to one of her clients, for example, and then they could spread the word to the rest. So I don't think her behavior is very polite. (Regardless of the reason, again). Lack of communication is usually a choice, not a force majeure. But that's just my opinion.