The retired lady, with nothing to do with her time all days, will sit back and scheme about the interaction. She will decide you are an adversary, disrespectful man who needs to be put in his place after 'abusing' an elderly citizen and a child.
You have maybe 1,2 free hours a day to deal with unexpected things that come up. SHE HAS ALL FUCKIN DAY. She will calculate and connive, and avail herself of every authority and ear and talk to them like a sweet concerned grandma who is bearing witness to an evil child abuser. And they will believe her. Every lie she spends 5 minutes conniving, will take days to months to disprove while CPS tries to comb through your personal life.
You have a kid and thus exposed to CPS complaints at anytime. She has no underage kids. You have a job to lose. She does not.
In any verbal conversation, you are the automatic loser. In any physical confrontation, you are the automatic agressor. You cannot win. Literally the only way to win an argument with an elderly lady is to walk off if the situation doesn't call for polite chit chat.