Stewart, the 26-year-old daughter of singer Rod Stewart, and Torriero, 19, are engaged, People magazine reported Thursday. Torriero's spokesman, Jack Ketsoyan, confirmed the couple's plans to the magazine.
Stewart also confirmed the engagement to Us Weekly, saying, "We're getting married."
They announced their surprise engagement Wednesday evening at a Los Angeles party for Microsoft's Xbox. Stewart flashed a 5-carat diamond engagement ring, according to People.
Stewart and Torriero, who have been dating for several weeks, were recently in the news as the back seat passengers of Paris Hilton when she was involved in a minor car accident Nov. 9. No one was hurt and police said no one was cited after the mishap.
Stewart is a close friend of Hilton's and was at one time reported to be a possible replacement to Nicole Richie on the canceled Fox reality show "The Simple Life."
Torriero, who stars on the MTV high school reality show, has said he's attempting to start a music career.