I would have a chat, but not at parents' evening.
It's hard to tell if she's really shouty. I used to do schools workshops & couldn't ever be a teacher - I rate teachers, they're brave. 2 incidents have stuck in my mind for years tho.
1 school where there was constant, low level talking in classes. I was only there 1 day yet it massively irritated me. Kids that just don't shut up.
I asked a teacher how she coped..Her face was so weary and fed up as she turned to me 'Its like this all the time. It never stops. I can't stand it much longer'. She did raise her voice during class but if she hadn't, she'd not have been heard.
Another where a teacher was so lovely in morning as pupils filed in. I went past his class later as couldn't find hall, and stopped in my tracks. He was addressing whole class in such a harsh, angry, bitter tone. They hadn't done wrong - he was just threatening them not to do wrong. You could see some kids literally shaking. They must've been 5-6 years old. I wish I'd said something but, what do you say? It upset me for days.
But the only way to know if there's an issue is to have a word. You've said other parents have mentioned it. You can gauge any reason behind it all when you have a chat...I'm wondering if there are constant talkers in your DCs class, leading to teacher having to raise her voice and tell them to be quiet.