I can’t quite remember all of this film, or… It was fairly long as I remember- so it may have been a miniseries. But I remember it starred a little girl. I feel like it may have been set in the 1800’s, and I think she was in a native tribe. But some other kid get’s bitten by what looked like a king snake- after that she runs off to a cave with her dog. She goes in and get’s lost, and the oxygen starts to get low. After that, her father (presumably) saves her and the movie ends.