My parents divorced when I was six. We saw our dad every Sunday. My mother said I came home a wreck after almost every visit--headaches, stomach pains, super stressed. No doubt if I had been T1 then, my BG would have been through the roof. Easy to say, much harder to do, but try your best to detach yourself from the reaction these people elicit. You can't change them, so you can only change the effect they have on you. Takes a real effort to talk yourself into not allowing situations to be harmful. I say to myself--been here before & I can get through this & am not going to allow myself to get sick. Meditation helps in calming & disciplining the mind. Only other thing, of course, is to take more insulin in those situations.
Shopping sends me low also. I think it's all the walking I do, getting more exercise than I realize. I get distracted shopping & have to force myself to test & correct.