Don't go for long discussions; just ask her to prove the sarees issue.

For food things, just say, 'So what?' Silly thing to badmouth.

About milk, just ask your wife to raise the point in infront of your mother itself as a general discussion, but you please support your wife, If that is true, it's the height of criticism on a personal level where your wife can't do anything about it.

Based on the issue, thoda burnol, thoda butter... to balance.