Heidi Montag promised The Hills' second season would be "much friskier" -- and with MTV scheduled to premiere the Laguna Beach spin-off's third season this summer -- she's reportedly doing her best to keep viewers tuned into the reality series.

Montag, a 20-year-old who The Hills star Lauren "LC" Conrad befriended during the show's first season, reportedly underwent breast augmentation surgery on April 2 at the Beverly Hills office of plastic surgeon Dr. Frank Ryan, according to Us magazine.  According to Us' "sources," Montag had been considering the procedure for "several years" and just recently decided to go forward with it.

"Heidi just doesn't want to make a big deal out of it," the source told Us. "She did this for herself, and she's hoping to keep it as private as possible."

The Hills' second season concluded last Monday night with Montag moving out of the apartment she shared with Conrad to instead live with her boyfriend Spencer Pratt.  According to Us, Montag declined to attend The Hills: Finale After Party at MTV Studios in New York City because Pratt was not invited.

"Lauren and Heidi are no longer friends," a source told Us. "They never talk or hang out. Spencer achieved his goal and broke them apart."  However Conrad said her relationship with Montag hasn't completely cooled.

"Of course, I love Heidi. I was in a similar situation with her last year when I moved out with my boyfriend [Jason Wahler]," Conrad told Us.  "Heidi and I barely talked, but as soon as [Wahler and I] broke up, she was there for me, and it only made our friendship stronger."

Montag was reportedly recovering from the breast augmentation surgery last week and could not be reached for comment by Us, but Pratt set the record straight on which girl rules The Hills.

"We're going to take over the world," Pratt told Us. "Heidi is the biggest star from that show."