According to the Cambridge English Dictionary, 'minx' means 'a girl or young woman who knows how to control other people to her advantage'; the Oxford Dictionary appears to have never heard of the word; the Urban Dictionary it means Cheeky or mischievous girl.
As I felt puzzled, I also checked internetslang.com (if there was to be any likely offender, it would be internet usage/slang) and they also say that minx is a cheeky or mischievous girl.
Am I looking in the wrong dictionaries 
Had my son reacted that way regarding a 23 month old little girl, I would have been seriously angry with him that he would think I would use a derogatory term for my own granddaughters - he wouldn't have left without saying goodbye, he'd have left with a flea in his ear for being so rude.
I also wouldn't tolerate him messing with his phone either - completely unacceptable behaviour when visiting, he might just as well say out loud that he'd bored!
You have absolutely nothing to feel bad about Thistledoo - you have used the word the way most of us would use it; you can't be held responsible for people who don't understand word usage.
How will the VAT cut be funded?
Missing certificate has been replaced but is it going to cause issues for sale?
You must be old if you have a purse or a wallet.
What was the name of the corner shop you went to as a child?


by way of apology - you don't deserve such treatment. 
