I would be honest and say it as you saw it. After all, you are a friend and if your friend finds you have mislead her about something, they may not remain your friend.
When attending any group, a childminder must provide suitable care for the children. Everyone works differently so what is a suitable standard of care for one person, may differ from someone else. Therefore, as long as no regulations were breached, you should not judge the other CM.
If/When your friend asks, then I feel you need to tell them:
Yes you saw her DS and his CM.
You saw him get told off for taking his shoes and socks off, and he cried, and he was put in his buggy.
Those would be FACTS, rather than your view. While he may have been ignored, without the full facts, it is only your view that he was being ignored, so miss that out, unless you have facts to go with it. For example, N was left on his own for x minutes.