Start with some plausible misinformation.
Doesn't have to be crazy or silly, just plausible. That way everybody wins. Your mother gets gossip about you/your family (albeit false information), and the go-between feels useful. Your privacy is maintained and you get to wear a $h!t-eatin' grin like the cat that ate the canary.
"Smile - it makes people wonder what you've been up to."