Pants? For what?

I was visiting the blogs which I love so much (one day I'll share the links) and found a very interesting picture.

Don't know which Olsen sister she is, so if you know, tell me. And it doesn't matter, though. I loved the pantsless grunge style. So cute and careless. I think it's Mary Kate, because she loves to go out looking as if she has less money than I do. Another picture (and now I'm sure it's Mary Kate) I love:

Well, she wore a long skirt, at least.