"I got my butt in the gym because, I said, 'This is the last week. You better be working out,' " the voiceover actress, 24, tells PEOPLE in an exclusive interview three days after the Feb. 4 finale. "So I didn't take any jobs and I worked out an extra couple hours."
But now $250,000 richer, Frederickson is ready to put the critical comments about her 105-lb. figure behind her and adjust to life after the ranch.
One thing she knows for sure: Frederickson is ready to step into the spotlight.
"I used to just be a voice over artist because I was hiding," Frederickson says. "So now maybe I'll put a face to the voice and come out of hiding."
"I've learned so many recipes and I've been cooking. So eventually I would love to start a blog and continue that communication with my fans and have a dialogue," she adds.
"Truly, the sky is the limit," says Frederickson. "I'm very, very excited about the future."
For much more on this story, including personal photos of Rachel through the years and interviews with former Biggest Loser contestants, pick up this week's issue of PEOPLE