If she does not not you have access or are reading her texts she might see it as a betrayal of her trust if you explicitly bring it up the texts with her.
I assumed he’s been up-front that he may monitor texts such that this is “monitoring” and not “snooping”. I agree, if he’s reading messages between D and Mom where D expected privacy, that would probably be interpreted as a betrayal, and would be good to resolve before it bites him.
