Which name is better: Camilla "Milla" Olivier or Jessa "Jess" Olivier? Any other suggestions?

For a story. Her brothers are Christopher (Chris), Zachary (Zach), and Nathan (Nate). Chris is 16, Zach is 14, and Nate and his sister (Milla/Jessa/_______) are 12. Thanks! I am open to all suggestions!