In The Twilight Zone episode "Ring-a-Ding Girl", I don't fully understand what happened.

Bunny Blake receives a stone that shows her the future. Following the visions from the stone, she goes home, and tries to convince the town to come to her one-women show instead of the town picnic. In the end, because of what she did, she managed to save them from dying in the plane crash, but Bunny disappears after walking outside in the rain.

I don't fully understand, if she was dead all this time, this means the crash already happened and all those people died, did she find a way to go back in time and prevent it? If so, couldn't she have just prevented herself from going on the plane?