The first actress to gross more than $1 billion at the box office, Julia Fiona Roberts, 33, has become one Pretty Powerful Woman, PEOPLE points out in its latest cover story. “As an investment,” Wall Street entertainment analyst Hal Vogel tells the magazine, “Standard & Poor’s would rate her triple-A.” Lately Roberts, who appears to be an Oscar shoo-in for “Erin Brockovich,” hasn’t been afraid to take financial risks. She waived her usual fee to costar with Brad Pitt in “The Mexican,” the $35 million caper flick which was No. 1 at the box office last weekend. In her next movie, “America’s Sweethearts,” Roberts plays a gawky minion to a movie diva played by Catherine Zeta-Jones, 31. Formula for a catfight? Forget it. “We have this banter. She imitates my accent,” the Welsh beauty tells PEOPLE from the set. “We’re having a lot of fun.”