Paris and Benji's Big Fat Fake Romance?

OK, now it's all starting to make sense.

Is Benji Madden hanging out (getting photographed) with Paris Hilton just to make his old girlfriend jealous?

Aussie singer/actress Sophie Monk reportedly broke up with him and now he's getting his revenge. Sophie told People mag that he most certainly did not break up with her!

So considering how fast Paris and Benji hooked up -- suspiciously getting photographed leaving a jewelry store with a ring and Paris coyly sporting a diamond B (for Benji or ...) necklace -- did a broken-hearted Benji ask his old friend for a bit of publicity?

'Cause, as we all know, there is nothing Paris is better at than getting publicity for herself and her pals!

Click HERE to get the inside scoop.

God, this is so "Gossip Girl"...

Photos: No real sparks for Paris and Benji? Benji with his ex-girlfriend, Sophie Monk.
WireImage

Additional reporting: Sal Morgan