Cry it out for naps?

First, I am posting anonymously because I know it’s a sensitive subject, so, if you are very much against it, please just move on and comment on something else, this is NOT what I’m looking for!

For those of you who have done CIO, or some version, has it worked? We are on day 4 of a modified CIO. Night time is 100% better, she does not cry at all, at the most 5 min. Now naps are not getting better! She’ll cry for a good 20-25 min and only sleep for 30 minutes. She’s constantly tired all day and I can tell it’s hard for her. Its been a very Excruciating 4 days for us both. Anyone had experience with this? I’m really at a loss! I’m ready to give up, but then I think, the last 4 days, I’ve put her through this for nothing. The mom guilt is so incredibly real.

She’s almost 6 months old

**edit - thank you for some of your posts! I started with 5, then 10, then 15 min, etc. But I noticed, that just seemed to piss her off more, the more I went in. So I’ve started waiting close to 20-25 minutes. She never goes past that, but, I don’t get that she does so well at night, but not for naps. It is in a darkish room, but you can only do so much about that. When should self-regulation kick in?! 😩