Are whines and cries for every need and attention hard for your nervous system?

I think the answer is just biology . Your so intertwined

Have her breathe. Teach her how to take a deep breathe, hold her hands and tell her to take a deep breathe and do it with her. It’ll usually help them calm down quickly and stop.

Yes, and this is really normal. I've heard it explained like the human brain can't tell the difference between a tiger attacking you and a toddler crying. Its because they both activate the flight or fight response. You'll want to come up with some in the moment regulation for yourself, and sometimes you may need to remove yourself (when she is in a safe space) so you can regulate. Keep doing research on regulation for yourself and co-regulation for her. You're already doing an amazing job. I didn't co-regulate with my first 2 children because I had never heard of it. It's newish in my home, and I still accidentally jump back to old ways, but breaking the cycle isn't supposed to be easy. If it's hard, you're doing it right.