Is it a Mary Sue?

Thunder Heart (MLP)

Is it a Mary Sue?
Thunder Heart

Name: Thunder Heart
Age: 9
Gender: Female
What Series it's From: MLP
Looks: Light blue with a yellow mane.
Personality: Adventurous and brave. Usually that takes the lead in a group she made with Blue Rose and Golden Moon. Is sometimes cocky.
Important Backstory: It keeps changing. XD
Likes: Golden Meadow, Star Chaser, Lightning Cloud, Melon Seed, Golden Moon, Blue Rose, thunder, Winter Snow, and Storm Light.
Dislikes: Blood Lust, doing nothing, reading, and school.
Parents: Golden Meadow and Star Chaser
Siblings: Golden Moon
Strengths: Can easily take the lead and is hard to scare.
Weaknesses: Doesn't know when something is too dangerous.
Cutie Mark: A heart with a lightning bolt going through it (she hasn't gotten it yet, though).

Please tell me if she's a Mary Sue! I don't think so but I'm not sure. OC is mine btw. Bye!