I'm going to assume that both Holly and ZA were there. Furthermore, I'm going to assume that Karen might have been there, too, and that information is being kept quiet (for whatever purposes).
If Karen had noticed ZA stalking her daughter, perhaps she did go up to ZA and say, "Zack, I'm Mrs. Bobo your fourth grade teacher. The girl you are talking to is my daughter, and you're making her uncomfortable. Please leave her be."
At some point during the evening, maybe he told Holly he would pay her a little visit sometime. Because now he knows who she is and where she lives... Maybe that's why Karen flipped out when she heard what was happening. But the information wasn't shared with Clint.
If Karen had noticed ZA stalking her daughter, perhaps she did go up to ZA and say, "Zack, I'm Mrs. Bobo your fourth grade teacher. The girl you are talking to is my daughter, and you're making her uncomfortable. Please leave her be."
At some point during the evening, maybe he told Holly he would pay her a little visit sometime. Because now he knows who she is and where she lives... Maybe that's why Karen flipped out when she heard what was happening. But the information wasn't shared with Clint.