I prioritize leveling/evolving the girls with character quests first. Their specific equips are really nice, especially since they have two bonuses and you won't likely have every equipment slot open on these 5* girls for quite a while. So far I've done Orchid Wydler's and as soon as I can evolve St. Paulia I'll finish her questline. Then it's just a matter of waiting to draw a Toad Lily so I can round out the set.

I hope they expand this in the future to include character quests for all 5* girls.