One has a look at her and you would swear that Sarah Jo, the wide-eyed protagonist of author/director Lena Dunham’s inquisitory and step-by-step disarming “Sharp Stick,” is not any older than 15. However regardless of her unadulterated smile, the fantastic thing about untainted innocence, and porcelain-doll garments with loads of bows, florals, and appliques, she…
