Sorry this is long
I have this and I wish it wasn't real and I wish I didn't have it, I have it as far back as I can remember, quite a young child. There is no official diagnosis but I do remember seeing a psychologist as a child speaking about these noises and stories my mother told me regarding my behaviour as they didn't know what it was and why I was so angry and would cry all the time with certain noises, it was only in my 20s that I looked into my feelings around this and discovered misophonia.
Different noises are different triggers for us, a person who is a loud eater will be extremely loud to us, a loud eater will sound like they are breathing really heavy through their nose, loud smacking, licking, crunching sounds will be what we hear. Unfortunately we don't choose who annoys us, maybe being around another person more than others we zone in on their eating, my dhs eating annoys me more than my adult children, but one of my brother's annoys me more than my DH, he sounds like he's eating glass when he eats.
Eating and heavy breathing is my worse triggers, there's many but these two are the worst for me. Bag rattling , sniffing, coughing and screaming a close second. I can't be around anyone who's eating an apple as it sounds like glass going around their mouth, eating a banana as it sounds like smacking, slurping nose, crisps are just a definite no with everyone, the bag rattling then the crunching, these actually make me extremely angry, I can feel my heart racing and the blood boiling inside me. These sounds are always extremely loud in my head.
I have gone through everything from quietly seething inside on the verge of hitting someone, storming off, shouting, pulling at my face and ears and head, wanting to punch myself and other people. I'm not a violent person but when these noises happen I am a completely different person. I have gotten off buses and trains mid journey because of the noises from people. I have walked out of small staff rooms in jobs and many more places.
My family know how I am, there's been many talks, arguments over it. I can look back now and understand why I was so angry in certain situations, unfortunately I'm now in my 50s and have suffered all these years and just wish people believed it's a real thing.
Doctors prescribed antidepressants but they didn't help, it's a case of finding which are the triggers and having a plan for coping in place. I have all sorts of ear/head phones, I can cope using ear buds at home with music to drown out certain noises and when I'm on public transport I have to use noise cancelling headphones that nearly suck my ears in with no gaps. It's not wide open spaces it's small enclosed spaces that is the worse for me. Wide open spaces seem to always have other noises that don't irritate me, for dinners here I wear wear buds, or just having the TV on helps a lot. If someone is eating or drinking in the same room and I'm not, I just leave the room and do some else.
I understand that it's difficult for others to not be offended and get angry themselves with people like me.
Something I discovered 2 years ago is ASMR, there are thousands of videos online on YouTube, it's trial and error doing this one but your DD might like to try it, there will be sounds she knows she dislikes but there's no harm in trying it, different sounds work differently for us all, while I may dislike the sound of running water, someone else will find it relaxing, there's every sound on there, have a listen to them and see if there's a sound that relaxes her, when she finds the sound(s) that doesn't irritate her and relaxes her it can come in handy to listen to it for the times she's struggling with noises around her.