And I'm mostly crediting this to how jealous is written in other works, but jealousy is a hard emotion to write. If a male character is written as feeling jealous, he's usually also written as super possessive and toxic. The jealous outbursts usually end in violence. On the other hand, it's a valid emotion. If Person A isn't taking Person B's feelings into account with their interactions with Person C, it's not unnatural for Person B to be jealous.
In the story, Character A makes friends with Character C. A hasn't had a lot of experience with social interactions, so she doesn't pick up on the fact that B is jealous. There is a magical element in play but it's very minor. Any tips on how to write the jealousy as believable without it coming across as toxic? (I know I won't be able to please all readers but I want this moment to be a low point of the relationship that they work through like a healthy couple.)