I would tell her that we all make mistakes and not to get too down on herself about it. I would encourage the person to work on responding to the child more quickly and build up the trust and attachment.
My older ds now four was adopted from Russia at ten months old.He was most certainly cio when at the baby home. I can offer your friend some hope.He is a happy little boy who loves his cuddle time at bed time.The ten months of cio is no match for the years of love and attention he is now getting.
I would tell her that she is a great mom for seeing what her child truely needs. No mom is going to make the right decisions all the time. But that she is an awesome mom for seeing and learning from her mistakes.
Most of us weren't raised on AP and we grew up with morals and the desire to make the world a better place for our kids! She was doing what she thought was best at the time. And that's wonderful, even if ow she would do it differently. Guilt is suffocating. SHe has to let go of it or it will affect her current parenting.
I think that I would say that we all do what we think is best at the time. And then later we find out that its not such a good idea. We can't help that. There are alot of examples in history of that happening. So, CIO can be another example. If someone has practiced that and didn't have access to literature that it was detrimental, then they couldn't have known and shouldn't beat themselved up about it. Its just good that they have learned and want to change.