You came up with an interesting plot move. Obviously, this is the mainspring of the story. However, the psychological makeup of your characters is not complete and that’s why they come out somewhat wooden.

For example, it is not clear what Mary’s exceptional drive was, why Brian was so impressed? Yes, you have stated that this was so, but it would be better if you would show it rather than tell it. This way I as a reader would make my own conclusion.

Ok, then… it is not clear why did she mess up so badly? Obviously, her preparation was good as she did it together with Brian: numbers were solid, the projection equipment worked, PowerPoint presentation looked dazzling. What was her mess up? Was she too shy, inexperienced? Didn’t she do any other presentations in college?

Ok, that could be construed as having some defects, but not a complete failure. Again, the same problem, as a reader I cannot see what happened and have a judgment of my own. As if, you are holding my hand and say: “No, pupils don’t go there. This is only for seniors.”
Next, not coming to work, just like that, without stating the reason? That sound too unrealistic. A person can be fired for that. More likely, she’d call to work sick.

Next, it isn’t clear what was Brien’s true motivation. You are giving some hints as he likes her – she’s an attractive blond, no matter how she’s dressed. Maybe that was indeed the reason why he spent so much time with her. Hoping that eventually she’d appreciate his help and attention and become his girlfriend.

Yet, as an author, you deny this, stating that his interest was completely professional.

I think as an author, you should make up your mind, one or another. If it was a professional interest only, then no need to mention how cure she was in her pajamas, as this implies that he was moved by a romantic interest.

This is just a very brief review. If you want I can make a detailed one.

Good luck to you!