I don't understand much what is she exactly doing >.<'' Why would she make that face?

She's most likely a fujoshi, in other words a female otaku who is into (and producing) yaoi and/or yuri.

Which, judging from the content of such works should explain her face.

I think it's more likely that her face is a result of sleep deprivation - see the translation note.

Is she wearing a skirt over pants/jeans?

My first thought was that it was the hem of her shirt, actually. I've seen shirts like that.

Her hairstyle is awful.

This seems more like a typical Mangaka rather than a fujoshi...

im damn sure shes hammering the buttons ctrl+z on the keyboard, which could also partly explain the annoyed face expression

I prop my foot up on shit like that too when I'm on the computer. I thought I was the only one.

kirikokku said:
I prop my foot up on shit like that too when I'm on the computer. I thought I was the only one.

i do it too. big plastic box on one side under my desk for if I want to sit sideways one way on my chair, unused computer tower on the other side for if I want to sit the other way