I’m looking for a family movie about teens from 80s or 90s. It was about a group of friends, probably early teens. One of the characters had a younger sister on the autism spectrum who wore blonde pigtails. I remember a scene where she came into the boys’ room, sat on the bed, put her thumb in her mouth, and started bouncing up and down. When one of the boys pressed a key on the computer, the girl screamed and covered her ears with her hands.