That rankled, although it was not precisely Snape's fault. Emmeline had dealt with the after-effects of what had happened to her by pushing herself to be better, stronger, so that no one could get the better of her again; hearing that he'd made the calculation based on the fact that he'd expected her to get out of it only reminded her that she'd failed. That was one of many things she tried not to think about.
"Perhaps we should try to work better together," she suggested. "I don't believe that we can defeat him if we're not united towards a common goal, and collaborating on our plans." Of course, there were also ways in which those could go wrong. But if they had fail-safes against anyone failing in their part, it couldn't go terribly badly.