Originally Posted by Saertis

That's if you consider only 3 target aoe girls and single target ones. But there're also 2 target aoe skills. That way it can happen that single target girl attack enemy hit by both 3 and 2 target aoe girls instead of go for that one who wasn't hit by later type of aoe skills. That's definitely not beneficial.

It makes no difference in that scenario though, if they aren't capable of killing. If you reverse the orders of attacks without changing the targets, the single target will hit the one enemy and then the AoE girls will double up on it and the end result is the same.

A scenario where it does help to have a single target go before the 2 target is this: let's say you have Orchid and Edelweiss vs 3 pests, two strong and one weak. Your Orchid can kill the weak pest without Edelweiss's help but neither of them can take down the strong pest in one turn, even if they both attack it, and Edelweiss can't kill the weak pest on her own. So the optimal targeting is Orchid vs the weak pest, and Edelweiss vs the two strong ones.

If Orchid goes first, the probability you will get optimal targeting is 1/3 (Orchid picks the right target) * 1 (if Orchid picked the right target, killing it, Edelweiss will always AoE the other two)

If Edelweiss goes first, the probability you get optimal targeting is 1/3 (Edelweiss picks the two strong pests) * 1/3 (Orchid picks the weak pest) = 1/9.

So in that very specific example Orchid before Edelweiss gives you better results. In general though I would recommend AoE first as others have said.