I mean it in the nicest possible way, you have to take control or your daughter she is going to learn how to walk all over you as she grows up.
You cannot seriously think it’s ok to drive with one hand?
How do you get a squirming, screaming, back arching toddler in a car seat? You pick them up, plonk them in the seat, you wrestle them into position and get the straps on. Yes you may have to force them into position, they don’t want to be restrained. It’s a toddlers worst nightmare, they have to sit in it for their safety and you can try and remind them of this. They won’t understand though but over time it may sink in.
I wouldn’t reward bad behaviour, I would praise them if they do it without a fuss.
Soon they will realise they have to sit in a car seat and will go in of their own volition, but until then you have to take control.
Meanwhile please know we have all been there, had to listen to them scream blue murder, almost put our backs out and feel like we’ve been wrestling a small bear each time we’ve put our toddlers in the car.