It reads to me that she did a favour, she looked after your children, she tried to discuss with your DH what had happened, which doesn't align with his view of the children, so became defensive.
She's tried to discuss it with you, ans you've been defensive.
No it doesn't need to be that way, not at all.
Your husband "not my childed!" Your friend who was obviously quite a trustworthy person to have been in the situation where she was supervising them without you or DH there. TBH there is a way of accepting criticism of your children's behaviour that doesn't tar them as awful human beings. "I'm really surprised at that, I've never seen that in him/her, that's really disappointing, we will need to have a discussion about that, as it's unlike them! Get to the bottom of this new reaction- blimming kids eh! I'm sorry they were trouble for you" we will definitely have yours back at x opportunity!
No point in getting butt hurt, even the nicest kid can be a little shit sometimes. My DD, sweet, kind, lovely, DD told me there was a very naughty kid in her class, no one knew who it was- was scraping the paint off the toilet wall. We discussed it at length. She was only 5 at the time. I told her not to be friends with the child who did it, obviously not a nice child.
Turned out to only be DD didn't it.turned out she was being bullied at school and would go into the toilet and scrape her nails on the walls. I'd have put money on it not being my DD. The point is our kids surprise us.
And tbh; I'd not necessarily take Uxbridge with someone finding DH defensive. If they just didn't like my children or my husband yeah I'd be of that opinion, but if your friend was trying to talk to you about your DH being defensive I'd have probably said, yeah he does maybe have a bit less of an ability to not become defensive with himself and the kids, but we all know neither men or children are perfect! Hes very grateful that you told us, but I think its hurt his ego that there's any idea they're not 100% perfect, he just has to acclimatise to the fact that children have a monstrous streak!
It doesn't need to be savagery from her part, or yours.