Board Thread:General Discussion/@comment-28792888-20140713234151/@comment-24891101-20140714064445

Her first substantive strike (by which I mean her second one, the first being to get out of its way) seems to be aimed for the neck, right above the primary cephalic scute. Its spine is also unarmored, so she was probably going for the cheap kill, and trying to prove her worth by making the kill in a single decisive stroke, thereby vindicating both her training (her form is perfect) and her prowess.

As to the other, Weiss probably singles out Ruby because of what she says: "Represent team RWBY!" Given Weiss' hangups in this episode regarding leadership, she probably resents what could be construed as Ruby rubbing her face in it, with the homophony of Ruby and RWBY. And her continued encouragement is distracting; "I'm trying to focus!" clearly carries undertones of "Shut up!", which Ruby doesn't get (Blake and Yang say nothing during the match). And then Ruby seems to give her an order, which she has issues with and is distracting, even if it is sound advice.