The 24-year-old, who plays Summer Roberts, let SELF in on her healthy habits, the philosophy she lives by and her biggest beauty blunders.

For the rest of the interview—including Bilson's not-so-secret guilty pleasure—read the cover story on page 36 of the May issue of SELF. Watch The OC at 9 P.M. ET April 27 on Fox and find out who will be prom queen. For more inside scoop on The OC, click here. Plus: Enter to win a trip to Los Angeles and a $500 shopping spree with one of the stylists from the show.

SELF: Now that you're a star, do you still have "Holy crap! I can't believe this!" moments?
Yeah, totally. It's the best thing ever! I was at the Marc Jacobs show and Sofia Coppola was like "I'm obessed with The OC," and I was like "I'm obsessed with you!" That was so exciting for me. I can't believe she knows who I am. That was my coolest moment so far.

Is it hard working and living with someone? [Bilson lives with OC costar Adam Brody.]
You'd think so but working together and being together is kind of nice. You'd never think it, but you really can see if you're compatible or not.

Do you ever feel like, "OK, I need alone time?"
Not really. You want your friend time because you're a girl and you want your girl time, but it's never like I need time away from this person.

Does food affect your mood?
Oh, yeah. If I'm hungry I'm a monster. I get so grumpy if I don't eat. I always have things in my purse, especially candy. I love candy. But I'll also have granola bars. I'll be at a party and I'll have an apple in my bag or cookies or crackers.

Do you follow any sort of eating plan?
No, I snack a lot. My favorite thing isn't a meal. I love junk food. Snacking on cookies or chips is my favorite lunch. But I also absolutely love fruit and vegetables. That's what I crave the most, actually. A really good nectarine or apricot. Anything really. And I'm a huge cereal person. I eat that for meals a lot.

What kind?
I love Cinnamon Toast Crunch, Life, Frosted Flakes.

Do you like to cook?
I love to cook. I'm getting more and more into it and I'm buying more cookbooks.

What do you make?
Breaded chicken. We had a dinner party and I made chicken tacos and homemade guacamole and all that for everybody, which is fun. I like cooking for people. I'm thinking of more meals to make. My mom got me a Rachael Ray cookbook. I'm not really ready for the whole gourmet 20-hour marinating. So I start out easy. I'm working my way up there.

Have you ever done crazy things in the name of beauty?
In seventh grade I used Sun-In to dye my hair and it turned half orange, half black. I was young. Then I did streaks during one semester in college and my dad called me a tiger's ass because it was striped orange. It was awful!

Do you have a philosophy you live by?
I believe that everything happens for a reason. I really truly believe that. The universe is so crazy how it works. I'm such a believer that what you put out there really comes back to you and the messages you send out in the universe. Like The OC: I was really close to getting this part on Everwood and I didn't wind up getting it and I was devastated. You take it personally. And then [the casting director] called me in for The OC, and if I had gotten the Everwood part, I wouldn't have been able to audition for The OC.

What's your healthiest habit?
Being honest. Sometimes I'm too honest and my friends get mad. You know, honest about anything.

Where did you learn that?
My mom, totally. Honesty is the best policy.

Has it ever been difficult?
Sure, in relationships. You do things you regret and being honest about it is hard.

Anytime when your honesty got you in trouble?
I think being honest is always the best outcome. Maybe it could be hurtful or some people don't want to hear the truth but the outcome is always better because after all is said and done, they know the truth and you can go from there.

How does it benefit your health?
I really feel like inside if you have any guilt it can really take a toll on your body, mind and spirit. It feels so good to have a clean slate.