Too, since you were leaving, they could have been picking up where they left off before you got there? Maybe "this" was something else and "she" was someone else. There could have been a phone call or someone else could have been there before you, etc.

Was the other student working on the same project? "With this" seems an odd choice of words if they were working on something else, her project or portion instead of yours.

He could have been berating himself, since he knew "she" was going to have problems; maybe he was disgusted with himself (as it sounds like he should be more often :-) because he didn't act on his knowledge and make sure things were running more smoothly.