Interesting plot development you have there, horror. Could be of use, perhaps I might add that the 'candies' that Erza has gotten from Porlyusica, that Erza has warned them not to take more than 'one'. Could be that after Wendy taking another pill, she becomes obsessed at getting even stronger?:P
As for your idea on Juvia, Levy and Lisanna, hrm, that can be mixed into all of this too
.