Name: Claire Cole

Hmm. Claire is derived from the French Clara, which comes from the masculine form of the Latin Claurus. It means "bright" or "clear" Interesting choice.

Age: 15 (start), 18 (ending)

Gender/pronouns: Female/she, her

Personality: sweet and kind, incredibly sensitive (often mistaken for weakness), but this gets overshadowed by her fear and selfishness

This is one of the only circumstances where your traits can conflict each other. When they're overwritten by bad things, and are reinforced by some sort of trauma (The Death Eaters)

Good traits: Enjoys simple things in life, loves his brother, always has a joke ready

Bad traits: She's a selfish coward, that by fleeing from the Death Eaters put everyone close to her in danger, but doesn't want to face the issue; rather she preferred living in the illusion that now she's safe. The "good traits" for the most part are a byproduct of this illusion

This is a really awesome idea. She is living in this false paradise, and almost her whole personality is centered on her backstory. 

Fatal Flaw: Selfishness

That's a pretty unique fatal flaw. People want their characters to be really likeable, so they make their character's fatal flaws something good. (Example: Percy's is loyalty, which isn't necessarily a bad thing.) However, you used something that's inherently bad, and I want to see how that plays out.

Hair color: Light brown

Eye color: right one green, left one light brown (caused by her powers. If she were a mortal, she'd have hazel eyes)

Skin color: Slightly pale.

That's what spending time in England will do to you. There's not exactly a lot of sun-bathing there.

Height: 6'1"

Weight: slightly above average, because of her above average muscle mass (not Clarisse-level, but still muscular)

Any malnutritionment from the death-eaters that could have had long lasting effects?

Godly parent: Ares

I've said this with Chris, and I'll say it again. Using Ares as the heroes godly parent feels like something Rick would do, but you're making it original.

Nationality: England

Weapons: -standard: her wand -full: her wand, steel kampilang (later converted to celestial bronze), 2x Desert Eagle (.357)

 Fighting skills: above average witch, average swordswoman, gifted sharpshooter

I like how she's not just a copy of Chris with a different backstory. She's unique, and even has unique skills (Chris is a total noob with the sword, if I remember correctly.)

Backstory: Kidnapped by death eaters at the age of 10. Brainwashed and forced to torture and even kill people, she initially refused, getting physically punished every time. At some point, she started obeying just to avoid that. When at the battle of the ministry she faces her brother and gets defeated, with a little divine help she remembers who he is, so she takes the chance and flees with him and other demigods, essentially putting them in danger of retaliation

Yes! This backstory is what's making her not completely hateable. Your readers must either be able to emphasize, relate, or have a strong attachment to your character, for maximum awesomeness. I can't relate to being hurt by death-eaters, but I can emphasize to it. I feel strong emotions to that character, and that's what makes a good character!

Mary Sue Rating: 0.9% (She's basically a hero with the qualities of a villain {not exactly an anti-hero} I'm pretty sure this is the lowest Mary Sue Rating I will ever give.)

Character Grade: 98.9%

Notes: Claire is an amazing character. A little advice, make sure to keep the story around Chris, but give Claire the parts she needs. Interesting doesn't always equal better. 

WARNING: MCU (Marvel) (Guardians of the Galaxy) ANALOGIES AHEAD.

Even though Gamora has a way more interesting backstory than Peter,

 (She was raised by the Mad-Titan Thanos, after he murdered most of her people, with a sister whose trying to hunter her down, who wants revenge because Gamora was better, and each time Nebula (the sister) lost, had a piece of robotic equipment that replaced a body part.)

, the movie is about him. Why? Because Peter is such a funny, amazing character, who also has a backstory that isn't fully revealed, that he's better for the audience. This was a mostly comedic movie. The audience got attached to Peter easily, and some could relate to losing a parent. They couldn't relate to having their dad adopt them and train them to rule the galaxy. And it was harder to emphasize to Gamora, because she was hunting down Peter, and had this wet-blanket mentality.

ANALOGY OVER.

Claire is a great character! But remember Chris, and don't forget him!