My little sister eats so damn loud and so MUCH, but my parents get annoyed when I ask her to chew with her mouth closed. Help?

I’m 15 and I probably have misophonia, and my noise sensitivity has only gotten worse since my concussion. My little sister is 6 and she eats with her mouth open, which wouldn’t be a big deal if she’d stop eating every once in a while. At home I can just go to a different room, but she eats in the car, too, and my earplugs that are supposed to block out those noises don’t do anything. I understand that from an outside perspective I’m just being a pissy brat when I complain about the noises, but it’s horrible, worse than physical pain in my opinion.

Usually when I tell my sister to chew with her mouth closed I just get an eye roll from my mom, which I hate but at least she doesn’t say anything. Right now, though, she’s congested and my mom snapped at me for asking her to eat her Doritos with her mouth closed. The thing is, she was watching Bluey, which is one of my favorite shows, but I feel a bit silly watching it by myself, so I didn’t wanna just go to a quiet room, I wanted to stay there and watch Bluey.

I told my mom that I chew with my mouth closed when I’m congested and asked how that’s any different and she said I’m still a noisy eater, but I don’t know how to not be, I ALWAYS chew with my mouth closed so I don’t understand how other people are even hearing it. Anyways, I went into the next room over hoping I could still hear Bluey without hearing the eating, but I COULD STILL HEAR IT. She’s. So. Loud. I complained to my dad and he told me I’m a noisy eater too, which isn’t fair because I try my hardest to chew quietly and will go in a different room if I know my chewing is bothering someone, but my sister never tries. She could chew with her mouth closed or she could just stop eating for once, but she just keeps making disgusting chewing sounds. I hate that I’m always at fault just because I’m “the sensitive one”.

What do I do when this kind of thing happens?