i would say, "hey aunt bella, wormtail called, he wants to know what time 你 want him to pick 你 up for 晚餐 tonight." then her response would be"i never agreed to go out with wormtail, eww." then i would reply"i know, i agreed for you." then i would run for it before she torments my butt off.
I think that Bellatrix doesn't need a lot to have happen before she gets pissed off. I mean really, you've seen what has happened in the movies. Seems to me, all 你 have to do is just speak when you're not spoken to and wala! 你 have a pissed Bellatrix!