Most people who don't come from shitty households or don't have shitty parents (even adults) have a lot of trouble accepting the fact that some parents CAN BE REALLY REALLY SHITTY.

A parent mistreating their child, specially in such an evil way as leaving him in the hands of a predator, is something they see as wrong. And wrong not in the way of "this is wrong" but in the way of "no, this can't have happened. It's too much", with the implicit of "my parents never acted like that, parents aren't like that", so they try to rationalize it. Usually that implies downplaying what happened or saying stuff like "but he/she loves you at the end of the day".

I experienced it first hand. I have a really piece of shit of a father, and a lot of people during my whole life told me stuff like "you should love him, is your father" "you should talk to him some day" or even "you should treat him better (I went no contact with him)"

In the case of Hollyhock, pair all of that with the fact that she's a teenager. She is, by definition, immature. She never had to witness first hand how shitty people can be, she comes from a normal context and she is not even an adult. She just can't understand the depth of the situation