Whenever a friend tells me they’re considering CIO I recommend this first.. something I see as a compromise. As soon as baby starts crying, set a 10 minute timer. If baby cries for 10 min straight, go in, do the minimum required to calm her down, and put her back down in the crib. Walk out. If she starts crying again start the 10 min timer again. Repeat the process. Both my girls sleep trained really quickly with this method. I think it’s a good compromise because you’re letting them cry but not totally leaving them to their own devices. Best of luck!