My daughter is just barely 12...5'7, 125 pounds. Tall, long-limbed, very strong. She is a right-handed pitcher, and bats left handed. That's what her dad did, so she copied .
I've noticed, and so has she, that her right quadricep muscle is more defined than the left. Not a huge difference, but you can tell when she flexes both. Her right arm doesn't appear to be bigger, but no doubt it is much stronger than her left.
Any thoughts as to what exercises we can do to even this out? Is it too soon for weights for her? The age seems too young, but her body may be ready.