LMAO, StormRider!
Hey Huesmann, they do? I'm not sure I would make such hasty generalisation. If you're experiencing that, then I think it's likely for any of these reasons:
(In all cases, she feels like she's in an awkward position.)
I) Maybe she has a secret to tell or something difficult to ask, but she's nervous. She asks you to get a feel of your mood.
II) You're a boring person. Once again, she feels awkward. She wants to get some conversation going. Of course what her conversation entails could be about her day or your day, feelings, etc.
III) She might just ask that in an awkward moment . . . maybe, for instance, she feels you're staring at her and would like to know why; hence, she asks what you're thinking. It presumes that you have her in mind, whether good or bad thoughts.