The (gentle) callout immediately makes Madoka's cheeks grow the same shade as her hair. Not that having been quiet to try and let someone concentrate is something to feel embarrassed about at all, but this is Madoka we're talking about. She gets easily embarrassed about anything.

It's even evident in her voice as she speaks up. "Sorry.. I just didn't want to bother you while you were working on it! It seems like such a hard thing to do.."

Or maybe that has more to do with her own lack of experience with it, huh.