Katherine Heigl is just being herself. That means she's finding it hard to make friends, even on set. From the National Enquirer:
Katherine Heigl "isn't making friends" on the set of her newest film Jenny's Wedding -- but the "little people" are finally fighting back! Production staff and crew are getting even with "Heil Heigl." Said the source: "Whenever she demands coffee, instead of using the sugar substitute and nonfat creamer that she orders, they're putting her under a secret fat attack by giving her real sugar and cream!"
Said an insider: "Katherine's extremely unfriendly to all the crew and production assistants, barking orders and treating them like servants. There's never a 'please' or 'thank you,' and God forbid you address her by her first name or make eye contact!" (Print Edition - 12/16)