This is a TV show rather than a movie, but the main character Rachel Berry is a vegan. (Just as the actress Lea Michele is vegan in real life.)

However, they go back and forth on this. In one episode she was apparently eating duck with her parents at a family dinner. ???

Glee tv show i am also watching. Rachel Berry is my favorite charter just because of he is a vegan

Even though the character says she is vegan, she isn’t. As pointed out a duck dinner plus she mentions she drinks milk.
Also when she leaves high school and goes to NY she tries cooking duck herself to impress a guy in season 4. Also in Season 4 she says she is vegetarian at thanksgiving.
Also she didn’t mind receiving a pig that was being raised to be slaughtered. Her only concern was that it wasn’t bling.

The actress Lea Michele is just following a vegan diet. So she isn’t vegan but a strict vegetarian following a plant based diet.
This is a common misconception with celebs.