If I generally trusted the stuff she had previously said about my parenting I'd be doing a lot of soul-searching to see if maybe she had a point, and post on MN to see if she WBU 
If she had form for being critical, passive aggressive or a narcissist, I'd be sending back a thumb's up or just the single word "thanks" and never mention it again, ever.
It’s very much the latter.
Unfortunately I didn’t ignore it.
It didn’t wake me up, my phone is never not on silent as my DM has form for texting at batshit hours of the night (it won’t have been keeping her awake or anything, she’s often awake at that time). But it was the first thing I read when I woke up.
My reply was “ I just love waking up in the morning to a message sent at 3 a.m. criticising my parenting. Thanks for that.”
Which according to her, was “nasty”.