Spencer Pratt has apparently succeeded in driving Heidi Montag away from her The Hills co-star and BFF Lauren "LC" Conrad and right into his arms.

Montag and Pratt are engaged, US Magazine reported Wednesday, adding he proposed to her Tuesday night at the Bacara Resort & Spa in Santa Barbara.

"She said, 'yes.'  She's over the moon!" a "source" told US.

The Hills' second season finale ended with Montag moving out of the apartment she shared with Conrad to instead live with Pratt -- which apparently disrupted the ladies' friendship, as Montag reportedly declined to attend The Hills: Finale After Party at MTV Studios in New York City because Pratt was not invited. 

"Lauren is just jealous of Heidi's relationship with me," said Pratt in the May 14 issue of In Touch Weekly.  "Until she accepts Heidi being with who she loves, their friendship is not going to work... Lauren's the one who wanted to date me first, before Heidi.  [Conrad] wishes she was in love."

The loss of Conrad and addition of Pratt in her life aren't the only major changes for Montag, as she reportedly underwent breast augmentation surgery on April 2 at the Beverly Hills office of plastic surgeon Dr. Frank Ryan, a procedure she had been pondering for several years.  Whether it led to Pratt popping the question earlier than he planned remains to be seen -- the couple has been dating for only eight months, but the two have been spending a good amount of time frolicking at Los Angeles beaches in recent weeks.

"We have so much fun," said Montag in the May 21 issue of OK! Weekly.  "I never knew I could love someone like this."

Montag, 20, and Pratt, 23, have yet to set a wedding date, according to Us.

"I'm having fun with Spencer, and we're looking forward to a fun summer," said Montag in the May 28 issue of Us.