Questions about my characters?

[dante]

Well, my friend and I are co-writing a story since we're both suffering from writer's block from our own stories.
So we had both created our own characters and I want to see what we can add or change..

The plot is still in a work in progress but it's modeled after the biblical story of Cain and Abel. A pair of twins (both girls) are part of a prophecy where they are said to be the opposites. They can either work together or fight against each other. It's a work in progress still, so it will be a while before anything is started.

Oldest twin (*my friend's character)
Name: Celia Shepherd
She has medium, curly chestnut brown hair with beautiful, amber brown eyes and a light tan skin tone. She is a social butterfly. She loves attention and is always with her friends. She is a popular girl that a lot of people enjoy to be around and she is a bit of a loud mouth. She will speak her mind and has a bit of attitude.

Youngest twin (*my character):
Name:
She has long, straight red hair with deep forest green eyes and pale skin tone. She is a loner, always hiding from everyone including her family. She doesn't speak much to anyone, often alone by herself. She is a beautiful girl but hides behind baggy clothes.

BQ:
- For the second character, would it be okay to name her Kerrigan?
- What else can I add to these characters to make them better?
- Should I change anything about them?