aio for worrying about my sister's headphone volume

my sister is 6 years old and neither of my parents care that she constantly has her headphone volume insanely high. i'm personally worried she's going to go deaf (i can quite literally hear the sound through her headphones, no these are not terrible quality headphones that easily leak noise either). i can sometimes hear her headphones from another room.

my mom says she doesn't think anything is going to happen because my mom listens to her music loud as hell and that woman can hear you breathing from across the hallway. i don't know how to feel about that, just because it never happened to her doesn't mean it won't happen to someone else but i see where she's coming from.

my dad does straight up does not care. the only time he cares is when she doesn't hear him, aside from that he could not care less about the volume. it's not even that he doesn't think anything can happen, he quite literally told me that if she goes deaf then it'd be her fault and she can buy herself hearing aids. he will do ANYTHING to stop her from screaming (which i'm pretty sure is why she screams so much in the first place) and got mad at me for asking him to care a little about the volume.

i'm 13 and stupid so i don't know if i'm overreacting, i've dropped the topic because it's clearly not getting anywhere and i'm just asking to see if i should actually stop worrying or if there's something wrong here.