If you mean Elizabeth I, she wasn't in any danger whatsoever, both were brought up in the new Anglican faith, introduced by their Father, Henry VIII.
Things changed however, when Edward died of consumption (tuberculosis) on 6 July 1553, and their eldest sister, Mary, was crowned Queen. Mary had been brought up a devout Catholic and believed her sister's Anglican faith to be heresy. She had Elizabeth placed under house arrest and came very close to signing her death warrant on a number of occasions due to Elizabeth's refusal to recant her faith.
When Mary herself died on 17 November 1558, Elizabeth was released from house arrest and proclaimed Queen. Her coronation took place on 15 January 1559