I think she was about 17-18yrs old when this happened. Keep in mind this was a blooper, not acutally part of the show. Basically in the episode, D.J comes back from her trip from spain and we are first introduced to her boyfriend Steve. Stephanie and Michelle become jealous of D.J.
Stephanie meets a boy in the airplane lounge who was flying to New Zealand with some choir. The boy invites her on the plane so she can say by to him. Next minute they are on a flight to New Zealand. When they return they end up grounded. Its now evening they are grounded Stephanie (jodie sweetin) is barefoot in p.j's and thats where the blooper started!