She may have played "Ugly Betty," but America Ferrera's next big dramatic role is going to involve a beautiful moment.

The actress's rep has confirmed to People and Us Weekly that she is engaged to her longtime live-in beau, director Ryan Piers Williams.

And just to make things official, the star showed up on the red carpet at the Edinburgh Film Festival in Scotland flashing her engagement ring, which perfectly complemented her black "tessa" tie shoulder Alice + Olivia by Stacey Bendet dress.

There are no details from Ferrera's camp on wedding plans or the ring, but jewelry and style expert Michael O'Connor tells StyleList it is approximately 2 carats and appears to have a vintage-inspired platinum setting with a round center diamond.

"This is a classic style that will look just as elegant 50 years from now," O'Connor says of the sparkler, which he estimates to be worth $50,000. "Since the diamond is set in platinum, America doesn't need to worry about losing the gorgeous stone."

Ferrera met Williams when he cast her in a film while they were both students at the University of Southern California. The couple, who set up house together in 2007, already share a dog, Buddy.

In other celebrity wedding news, read about the Hollywood trend of engagement ring downsizing.

And check out this disturbing wedding style discovery -- bridal diapers!