Wait, hold on. Ok, so there are 3 possible answers to this:
1. She is a little girl in a full grown body.
Q: How the hell did she not break her mom stomach open?
2. She has some type of mental disorder.
Q: What is this mental disorder and will we ever learn about it?
3. She might’ve had an accident and went back all the way to grade school.
Q: What was her life before the accident? Was she a swimmer? What happened after the accident before she met this blonde chick?