What is the mother-in-law teaching her children like this for?

In fact, what she does is to compete with you in front of the children.

Honey, in this case, there is only one way.

In front of her mother-in-law, tell her how good her grandmother is and how to be filial to her when she grows up. Grandma is the dearest person in the world.

If you praise so often, your mother-in-law won't teach you so.

If it is more serious, my husband will have to adjust.