When fighting with Flutter plume it is suggested to roll opposed checks. It also states she is Adversary 2. So how do you suppose that should work ?

Create the opposed check dice pool, and upgrade it twice for the Adversary 2.

Since she has a Brawn of 4 and a Brawl of 4, that means the dice pool starts at 4 Challenge (red) dice for anyone trying to grapple with her. Upgrading once adds a purple, and upgrading the second time makes that purple a red. So 5 red Challenge dice. Yikes.