By Rose Hill Jamie Lynn Spears has opened up for the first time about why she decided to spill Britney’s secrets while she was appearing on I’m A Celebrity. Initially, the actress and singer had appeared reluctant to speak about her world-famous popstar sister on the ITV show and remained quiet while others talked about their own families. However, she later opened up and told campmates about their childhood and offered behind-the-scenes information on Britney’s performance with Madonna and her Vegas residency. During tonight’s spin-off show, I’m A Celebrity… Coming Out, Jamie-Lynn will open…