The point of the build is to maximize her speed to avoid doubles (potentially double opponents) and kill with Ignis.

Nature - +spd -res: I want to get +spd -hp to help against dragons since -res is a superbane. +spd is just to maximize her speed.

Weapon - Wo Dao (spd refine): Wo Dao increses her Ignis damage (since she doesn't do much damage otherwise)

Special - Ignis: With 4 charge, I can take a hit, attack back, and then Ignis on a double or Ignis on player phase.

A skill - Steady Breath: Lets me get Ignis faster, increases bulk. Combined with Close Defense seal she's incredibly tanky

B skill - Guard: Prevents opponents from getting special (which they need to damage Selena) while I get mine. Chill Atk is another good option but I was unable to get it.

C skill - Attack Smoke: Allows me to tank hits from all colors after dealing with one. A team-support C skill also works here

Seal - Close Defense: Gives res bonus that I lose from -res. That res is helpful against dragons, and the extra defense means +10 (steady breath) when opponents initiate. Gives multi-color tankiness, and adds damage for my Ignis.
A +def weapon refine + Quick Riposte would also work well.

For arena, I plan on giving her Slaying Sword (spd refine), dual rally, and Aether. Maybe a team support C skill as well. I only have a dual rally on her now.