When does bonnie reveal her powers to Elena in vampire diaries?

In The CW television series "The Vampire Diaries", Bonnie Bennett reveals her powers to Elena Gilbert in the first episode of the second season, titled "The Return". At the end of the season 1 finale, Elena finds out that she is a vampire due to a car crash that also killed her parents and she is also falling in love with a 162 year old vampire, Stefan. In season 2 Elena asks Bonnie to help bring back Jeremy, her brother, who died as a result of the car crash. They are at the cemetery at the beginning of the season and Bonnie tries to bring him back but she reveals her powers to her by casting a spell to bring Jeremy back.