Feeling Rather Annoyed

My boyfriends 6 year old daughter will wet the bed if she has something to drink past 7. Well he decides at 9pm he's gonna let her have hot chocolate while they watch Hocus Pocus. I told him she's gonna pee and he said "Eh, its not an every night thing. If she does I'll wash it". I feel like he's being really irresponsible. He knows she will pee if she drinks after 7, yet he doesn't care and is just gonna let her.