How can I make her happy?

This has nothing to do with relationships, but I thought I'd ask here because you may have good ideas. There is a lady who comes into my work, a mail courier, she hurries in and drops of the mail, doesn't look at us, and hurries out. When we say thank you, she used to not say it back at all, she used to not speak at all, now she's starting to mumble "welc..", but still makes no eye contact. She just looks so sad. I'm fairly certain she is not just a bitch, I think she is depressed or some horrible life event happened to her recently. I want to give her a hug so bad and let her vent, but as this is a workplace that would inappropriate obviously. So what can I do? How can I add a little brightness to her day? How can I make her smile?