Sophie Monk's New Friends

Dating fraternal twins Joel Madden and Benji Madden, has been a bonding experience for Nicole Richie and Aussie singer/actress Sophie Monk. The two have been inseperable the past few weeks as the Madden brothers, both 27, have been on tour with their band Good Charlotte.

Benji just recently proposed to the stunning Sophie Monk, 27, on Christmas Eve, presenting her with a 3.5-carat diamond and platinum engagement ring by star jeweler Neil Lane.

While Nicole Richie, 25, and Joel have only been dating a short time, friends of the star tell Celebrity Babylon she is serious about her tattood boyfriend.

"She flew all the way to Japan last week to be with him," says the source, "she is really into the guy, it's serious."

For his part, friends say Joel is completely over his previous love Hilary Duff, 19.

"It's like Hilary, who?"

Instead of being with her recently reunited Simple Life BFF Paris Hilton, 25, Richie is constantly enjoying the simple things with her new BFF Sophie, like trips to LAX to send their guys off with steamy public make-out sessions, or sojourns to a vegan restaurant for figure slimming organic meals.

Could all this togetherness mean that there is a double wedding on the way?