Ignoring the religious elements, this is factually incorrect. Nobody likes to talk about it, but it's common for pre-pubescent girls to masturbate. George Carlin even had a bit about it!
Now, that's generally not talked about for good reasons--we don't want to rile up the pedophiles, and we don't want to rile up the people who are so aggressively religious that they can't acknowledge biology. But the fact of the matter is that people don't become sexual the instant they reach their country's age of consent or the instant they get married.
There's nothing wrong with you disliking those facts, but they are what they are.