|Est's new weapon allows her to punch holes in armors, as well as anyone else unfortunate enough to be caught in the weapon's effect.
'"`UNIQ--item-334--QINU`"' or '"`UNIQ--item-337--QINU`"' are the best options for this build. Assuming she has the weapon activation requirement met, she essentially has a 16 Mt Brave weapon; when combined with either of these skills, you get +12 or +16 total extra damage (depending on the skill used).
A number of B slot skills can be used here, but one good option is '"`UNIQ--item-340--QINU`"'. With this, she can safely dive into combat, and return to safety after. Alternatively, she can choose a breaker skill, such as '"`UNIQ--item-343--QINU`"'. With many of the game's sword units having 40+ speed, having this skill can help keep Est safe from heavy damage.
The C slot is flexible, but flier buffs are highly recommended since she'll need to be around at least 2 to activate her weapon's effect. '"`UNIQ--item-346--QINU`"' is a cheap, easy choice that's found on her eldest sister, Palla.
'"`UNIQ--item-349--QINU`"' is a powerful choice for a seal as it allows her to activate 2-turn specials such as '"`UNIQ--item-352--QINU`"' on that same turn, which would likely obliterate the opponent before they could retaliate. '"`UNIQ--item-355--QINU`"' is also a viable option; a flat boost to Attack never hurts.