The argument above seems to be that trading involves you dishing damage to her while she hits you. In the above scenario, she shields dps which you wait out (1.5 seconds is pretty long-ish in a fight). You're backing off and she heals as a result.
The heal combo shield makes it so that your output was reduced, but she still got dps and some of which probably was true damage.
Camille seems like the sort of target you should be teaming up against though, so without any other given factors... she turns into a very solid duelist and this is an example of that in action. Without some sort of gimmick, she will potentially win this fight if you don't have the raw numbers or CC to kill her.