I think it’s down to the sort of child you have.
We did a bit of cc with DS, who is the same age as your DD OP.
He’s generally a good sleeper and we co slept for the first year. But he’s big and heavy now and I found I was waking up with sore shoulders and a cricked neck from cradling him all night. I have back issues anyway and was just tired and in pain all the time.
So we did cc. Mainly in the middle of the night. DS’s cot is right next to my side of the bed (small flat) so he can see me, but when he wakes in the night I just shush pat him and then get back into bed.
The first night we had to listen to him screaming next to us for about 45 mins. The next night it was only about 15 mins. Then subsequent nights have been about 5 mins of grumbling before he goes back to sleep.
The thing is, in the abstract, cc and cio seem barbaric to me. I can’t bear to hear my child upset. It seems unnatural to ignore the urges to comfort them. And of course, if DS is genuinely upset, I scoop him up and cuddle him no question.
But I know my child. I know him really well. I can tell a tantrum from genuine distress. When he was crying during cc, it wasn’t because he was upset or scared. He was furious! He wanted to be in our bed. He preferred to be in our bed and until now he’d been allowed in our bed. How very dare we tell him no, you have a perfectly good bed of your own DS, sleep in that. Oh he was so cross! Really mad at us. That I can live with. But I wouldn’t feel okay thinking he might be scared or sad. Only you know if your child is the fearful sort, or the angry sort (like DS!).
It’s tough. Sleep deprivation is hell. And there is no one size fits all approach. There are some pompous, judgy twats on this thread.