By Lisa Ingrassia
February 06, 2009 12:00 AM

American Idol isn’t all fun and itsy-bitsy bikinis, says Katrina “Bikini Girl” Darrell.

Darrell, who was eliminated in the second round of Hollywood week, says exhaustion contributed to her poor performance Feb. 4.

The night before the group competition, instead of rehearsing with teammates Rose Flack and Jasmine Murray – other members of ‘Team Diva’ – Darrell, 20, chose to take a nap.

“The day before group night, we ended at midnight,” she told PEOPLE Thursday. “At midnight, we got the song … to learn, and we were supposed to be dressed and ready to go by 7 in the morning. I hadn’t slept in 48 hours straight. And at four in the morning, I said, ‘I’m delirious, I need to lay down for an hour.’ ”

Darrell – who earned her reputation as an outrageous contestant when she wore a bikini to her audition, making an instant fan of judge Simon Cowell – insists her decision to skip rehearsal wasn’t a cop out.

“It wasn’t like I went to bed and gave up,” she says. “I practiced a lot.”

Wearing heels for hours, she added, aggravated her scoliosis. “I really started feeling it because I was in heels for so long,” she says. “I was exhausted and my back was starting to hurt.

Darrell also believes she was at a disadvantage because new judge Kara DioGuardi “had it out for me from the beginning,” she said. “Maybe there was a little jealousy. But I wish she had given me the opportunity.”

Despite her early departure, Darrell enjoyed her time on Idol. “It was a great experience,” she says. “I had such a positive response from Simon every time, it made me feel really good. He’s the one I respect the most.”

Darrell, who lives in Southern California and is currently working on a bachelor’s degree in telecommunications, says her Idol appearance has already lead to some offers for record deals. “I’m weighing which contract is the best opportunity,” she says, adding that she hopes to record an album with R&B and reggae vibes this year, as well as plan a tour.