High Arena Rating Skill Setup for Cherche?

I have a 4* Cherche with
an Attack Boon and a Speed Bane
that I've merged 6 times, which makes her as strong as an unmerged 5*

Im building her to make her worth a lot in the arena using this setup:
Brave Axe+
Draw Back
Aether / Galeforce
Death Blow
Wings of Mercy / Brash Assault
Goad Fliers

I think Aether would be more useful on Cherche than Galeforce would be, because every time Aether procs it heals Cherche.

For my B Skill:
Wings of Mercy is worth a lot of SP and makes Cherche much stronger on a defense team since I could get free kills off of careless players and she could protect my team, and Its still very useful to me when I'm playing.
Or
I could use Brash Assault, so when Cherche has 25 Hp she would quadruple enemies for 60 attack per hit.
But on a unit as strong as Cherche, does quadrupling even make a useful difference, or should I give her Wings of Mercy?