+def -atk Summer Young Tiki

Something like Ignis, Atk/Def Bond, Quick Riposte or Guard, and C skill of choice with either Iote's Shield or Quick Riposte in the seal would probably work well.

She's basically a physical wall with speed to not get doubled like A!Tiki without the need of a breath A skill. Go with her default A and possibly QR3 or guard3 for B. C is entirely depending on what kinda team she is gonna be on and finally her special works well in several ways. She has a built in breath in terms of special charging, so obviously aether is amazing, but any other skill like ignis or bonfire would work well too. Overall I would say her base kit is extremely solid, but her special and her B skill are what will determine how you use her. While -att is unfortunate, the fact that you have a free A slot can change that, where a distant counter user will have less attack unless they are +att when you run Att/def bond. Think of her as an amazing anti dragon physical wall with enough speed to even have a good player phase.