The singer and actress is one of the new judges on the US talent show along with rocker Steven Tyler.
Asked how it's going, she said to Access Hollywood: '[It] has been like sitting there and watching the show for five hours a day, which, hello, how else would I want to spend my days except in bed watching American Idol all day? It's been so much fun.'
She also spoke about her reaction to when contestants try and sing some of her songs.
She said: 'Sometimes it's great, and sometimes it's like: 'Oh no!' But it's always entertaining.'