I didn't think of this before but years ago when my children were little and I didn't have time to do anything, my Mom came over one day, saw a lot of dust around, and picked up a cloth and started dusting, and as she did, she said, "I know your mother-in-law couldn't do this, but I'm your mother so it's ok." I know she meant well.
I thought, "Well, you can't either without making me feel awful," but I never told her. I think it's just that mothers feel they can be much more verbal with their daughters than is really thoughtful at times. I've taught my four daughters to speak their minds......somewhere in there is a balance, LOL. I've found myself once or twice being too verbal but my girls make sure I know if I have hurt their feelings or overstepped my bounds. I'd much rather it be that way.