Speaking on behalf of the boys, Jamie Durie said: "We were all just so taken with all of your performances, they were absolutely mind blowing."
"The transformation from day one to now, has been phenomenal. This has been a very, very tough decision."
"But unfortunately there can only be one winner... and it's Jess! You were amazing."
She battled against fellow contestants Stephanie Rice, Anne Edmonds and Anna Heinrich to take the role of Baby.
Jess will play the role alongside Hugh Sheridan, who was chosen by the ladies on Monday night to play Johnny.
"Thankyou!" the TV personality said, after she was told she'd won.
"I'm so overwhelmed. It was the furthest thing from my mind that this would happen. I can't believe it."