When a child humps, should she be allowed sleepovers?

my four yr old has the " syndrome". when she was younger she would hump the car seat, then it was the high chair. she's never been left alone with any guy, and i thinks its very unlikely due to inappropriate touches. shes very curious in the female privates as well as the males. once i took away the car seat and high chair and replaced them with regular chairs, and booster seats, it seemed to have stopped. now its the stuffed animals. this is kinda frustrating for me as a first time parent. everyone says its normal, but it feels very scary to be experiencing this so early on. she has kissed a boy in preschool. aside from saying "no, and stop", s dont work. i stopped giving them. i stopped saying no, and stop. now im going to take the stuffed animals away. sleepovers, how do i handle them? i dont want her to show other kids what's she's doing, or to try ual explorations with them, or them with her. what the heck do i do?