I had an aunt once say to me "Do you know you have a double chin?" not long after my first child was born. I didn't, but I was a little fuller in the face, a bit of a softer jawline than before I nearly died giving birth, for sure.
My response was to look at her incredulously and say "Do you own a mirror? Do you know you've had a double chin for 40 years and I've never said anything?!" Yes, I really did say that. I don't do well with being attacked, and that sort of rudeness is, indeed, a verbal attack - however it is couched and regardless of the tone. She mumbled something about "oh not 40 years..." I mean she was right it was more like 20. My mum actually laughed (her sister).
I'll never understand why anyone puts up with cockwomble rudeness, it is just not in my nature, any more than it is to take a slap from someone. Slap me, you are getting slapped back.
I am always as nice as pie, genuinely pleasant, to those around me, good natured and polite and I don't take offence if I feel someone just slipped up or didn't mean to be offensive. But when someone is being deliberately rude, as your aunt is - no. No. There's no need to put up with that nonsense.
Sweets to the sweet, cunt to the cunty works very well for me. Of course, you do have to have a good firm grip on your own self worth and no interest in being a doormat to "keep the peace" for this to work. And keep the peace always means other people's peace, of course, not your own.