I am in level 5 French, the lesson about extended family member names. It said that "Le Bébé" is always masculine. Does that mean when I refer to my toddler niece, I refer to her as "le bébé" not "la bébé"?
Yes: some words have only one gender despite the gender of the subject, of which le bébé is an example, as the lesson stated. Another example would be la vedette (the star). So if the star of a film is male, he is still referred to as 'la vedette' (e.g. Alan Rickman est la vedette de ce film).