From what I've heard from friends who have had the opportunity to go meet or work with her, Foster is extremely kind and gracious. Just because she DARES to not stagedoor doesn't mean she's gotten a big head.
Some performers can be perfectly wonderful people, but find the stagedoor scene uncomfortable. It has nothing to do with whether or not they "appreciate their fans". Not everyone enjoys being mobbed as they exit the theatre.
Getting an autograph and photo with the star is not included in the ticket price. This is their job. Is it great that some high-profile performers take time out to sign and take photos? Yes. But it does not make someone egotistical or rude if they don't.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."