Jamie-Lynn on Ex: 'There's No Hatred'
But it was also a period of sadness, with her two-year marriage to her manager, A.J. DiScala, 35, ending last September. That wasn't the first challenge Sigler has had to face. When the actress, who lives in New York, started on the HBO series in 1998, she was struggling with an eating disorder, which she's since gotten under control.
"I've definitely been in the public eye during years when girls go through a lot of changes," she tells PEOPLE in its latest issue. "But I'm more confident now in the person I am."
On suddenly being single
"To come from where you thought your life was set – that this is who you're going to be with, that you're going to start having children with him very shortly – for it all of a sudden to kind of all not be there, it's scary. I met A.J. when I was 19. We started dating when I was almost 21. But from the day I met him he was the man in my life. So I basically went from being in high school and having my parents take care of me to A.J. being that caretaker.
"Now, being 24 and single again, you learn a lot about yourself. This is the time to find out what Jamie wants. Who Jamie is. But with A.J. and I there's no hatred, there's no anger. I still love him very much. I know he loves me. It's just what's best for both of us."
On her friends Nick and Jessica
"It's funny, 'cause A.J. and I, when we met Nick (Lachey) and Jess (Simpson), we really bonded because we were both these young married couples. And it's kind of ironic that we both separated in the same year. A.J. and Nick are extremely close, and Jess and I are close, and we all respect and love each other just the same."
On starting the Jamie-Lynn Sigler Foundation, which helps girls with eating disorders
"I was mentoring a bunch of girls at this treatment facility in Malibu and we still keep in touch via e-mail, but one of the girls who was in the house had to leave, in the middle of treatment, because her insurance ran out. She's not doing well now. I've heard of two people who passed away because of this. So that's one of the main focuses of my foundation (making sure those in need get help). I think people view it as this vain disease. But it's becoming an epidemic."
For more from the interview, pick up the latest issue of PEOPLE, now on newsstands.