It's the new American dream: Reality-show stint leads to respectable acting career. Unsurprisingly, there are few success stories, but Jacinda Barrett has bucked the trend. ''When I did [THE REAL WORLD in 1995], there were no reality shows, so people [didn't] think you go on them and get famous,'' says the now-in-demand Aussie, 34, who followed MTV with some time studying drama at Oxford. It took a while to get Hollywood's attention; 2003's THE HUMAN STAIN was her first sizable role. But now she's leading-lady-bound, having survived POSEIDON and her most emotional role yet, as unfaithful Zach Braff's girlfriend in THE LAST KISS. ''I have never in my life been as angry as I was in those scenes,'' says Barrett. ''They were situations my friends and I found ourselves in.'' Comic relief came while playing Jon Heder's crush in SCHOOL FOR SCOUNDRELS (Sept. 29), and next year, she'll be seen in THE NAMESAKE, based on the best-seller about Indian Americans. ''Everyone in the cast spoke Bengali. I felt like an outsider.'' Not for long.