To infantilize her may be a shortcut to compassion ... but it's ultimately disrespectful to her, IMHO.
Then you completely miss the point of this way of viewing MrsHD. It is not meant in any way to get a one up position, to gain some level of control or to disrespect her. The whole point of viewing MrsHD is for HD’s perspective, to allow him a way to detach from her emotional outbursts and not be hurt by then, to weather the storm and still remain empathic to her hurts.
When a child is hurt or traumatized, emotional growth can stop at that time as the child shuts down and goes into self protect mode. So in this way MrsHD is still very much a child on an emotional level. That is why her actions seem so crazy. They are crazy from an adult perspective but they are not from that of a child.
Go read this website on Steve Stosny and his book “You Don’t Have to Take it Anymore.” I have the book and HIGHLY recommend it (I also have his new book but haven’t read it yet). Stosny describes very well why compassion is so critical in break out of the logjam so many couples get in and gives a way to do it.
