In this trope, Alice's prejudice towards Bob isn't something she came up with on her own. It was taught to her—maybe by her parents or guardians, maybe by society writ large—and she just accepted it as "the way things are" and never thought to question it.

Note that the technical definition of "prejudice" refers to "pre-judging" people, so this trope doesn't necessarily refer to beliefs that would traditionally be considered bigoted: Alice's dislike of Bob may be based on him holding a political or personal belief, rightly or wrongly, or they could be in a