No idea what board this would fit under...

So we recently moved to an apartment. We are on the third floor and have a neighbor who lives on the same level as us. She appears to be young, early 20s maybe. She avoids eye contact, barely speaks above a whisper if she says anything at all (I try to always say hello or have a good day when I walk by. She is out smoking frequently so I see her several times a day).

We live in the south and this is very unusual. She seems very depressed and sad. If I had ever seen a man around I would be concerned about domestic abuse, but so far I haven't.

Would you do anything? Keep being friendly? Stop saying hello? I dont want to pester her and I know people are all different, it just makes me sad to see her looking so sad and lonely every day.