How to explain antisemitism to a high schooler?

A (non-Jewish) friend’s daughter is trying to make sense of the broader world and she’s coming across some ugly truths such as bigotry in its different forms

Because I’m Jewish, I’m the guy this kid goes to whenever she has questions about Judaism. She recently asked me what antisemitism is, and I started off with a fairly basic answer (hatred of Jews). But she already knows that and wants a bit more in-depth of an answer

I’m trying to figure out what and how much to tell her. It’s a heavy topic and she’s still trying to make sense of everything else in the world, so I’m a bit cautious and wary of accidentally triggering an emotional overload (which I’ve seen with her and I want to avoid happening again)

This is the first time I’ve really had to discuss this with somebody her age, so anyone with experience or other advice on how to break down the subject in a digestible but not too watered-down manner would be super helpful

TIA