Sydnarella, your pet peeve is almost identical to mine...only in my case it's my great-aunt (89 years old).
"Have a cookie"
No thanks, I can't, it's not on my diet.
"Well then have some crackers"
No thank you.
"How about a piece of cake?"
No thanks.
"Here, have some nice fresh Italian bread"

This goes on & on, EVERY time I see her (at least once a week) and always winds up with: "What kind of diet is that, where you can't eat anything!?!?"