How do I deal with the eerie stare?

There is this woman who has a strange stare. I don't like to look at her and just avoid eye contact. She's an odd person because no one really stares like she does. It's like almost evil look and obvious. Her head turns almost eerily as you walk by. If you walk by she'll look like she wants you to know she's looking at you or something. She used to smile sometimes, but I think it was only when she was feeling good, then she'd ignore me and stare weirdly. Because I ignore her mostly, I walked by her not having a choice and she just looks like almost rolling her eyes...what the f is wrong with her? Other times I p by her and she just point blank stare, and I have to kind of look away because it's so weird. How do you respond to her strange stares? Do I continue to ignore her? I really don't appreciate it because I doubt she'd do stare at her boss weirdly. I avoid her to keep things just where it's at but not to worsen anything.