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Nikki Reed had a dazzling accessory to flaunt at Sunday's MTV Movie Awards in L.A., one which nearly upstaged her black Heather dress and Jimmy Choo heels -- an engagement ring!

The news may come as a bit of a surprise to some -- despite dating for less than two months, a source confirmed to Us Weekly on Monday that the Twilight actress and American Idol alum Paul McDonald are indeed engaged.

Reed, 23, flashed her sparkler on the red carpet and gushed to E! of McDonald, 26: "He's the one. He's the one."

Along those same sentiments, jewelry expert Michael O'Connor tells Us that the eternity-style ring is very appropriate for such a head-over-heels couple.

"This is a modern version of a platinum and diamond eternity ring that could also work as a stunning wedding band," says O'Connor. "It features full diamonds surrounded by intertwining platinum, and is a great symbol of two people bonding together for a lifetime. Estimated price tag: $30,000."

Just two weeks ago, Us broke news that the twosome were already living together in Reed's L.A. home; Reed (who briefly dated Twilight costar Rob Pattinson) has been trying to help her man land a record deal.