The sisters said they had "so much fun" making the movie -- and they were practically inseparable! "We got to drive to work together and shared a trailer," Hilary told ET at the premiere. She said the best part about making the film was that she and her sister got to "have fun and goof off."
There's no sibling rivalry here; Hilary tells us they never get jealous of the other's accomplishments. "We're really proud of each other," she says.
"We have a really close sister bond," Hilary says of their characters. "We have to work really hard for that to come across onscreen," she says with a wink.
I think they like each other and working together but it's a little late to compete with the Olsens. Lots more pictures of Hilary and Haylie looking fabulous at their premiere so