Tits are naturally sexual. We specifically evolved to have women's tits stick out all the time, even when not lactating (We're the only species on the planet that has always enlarged breasts) specially to attract males because sight became a much more important factor than scent (Such as going into heat).
And it's true, just having tits does not mean your character is sexual. But giving your teen character a shirt that always reveals a bit of the midriff and loosely hangs as a result of their chest bump is pretty sexual. On top of form-fitting leggings that accentuates their tall, curvy, thin legs.
Like, this character is designed to be extremely sexual despite being 14-years old. And it's strange that a liberal California woman would design that.