i would say, "hey aunt bella, wormtail called, he wants to know what time anda want him to pick anda up for makan malam 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 anda have to do is just speak when you're not spoken to and wala! anda have a pissed Bellatrix!