She's hardly doing this on purpose. I bet a jelly-filled donut that most of us have had sexual partners or known of people who at the critical moment let loose with the most amazing verbalizations. Some Buddhist sects believe that at the moment of orgasm, one gets a tiny taste of what enlightenment is like; is it any wonder that it inspires the autonomic nervous system to express itself freely?
And that, to me, seems to be an iron-clad defense. "Yes, your lordship, I farted long and loud, but even the emperor Claudius recognized that farting is an uncontrollable natural function which it is harmful to try to rein in." Mutatis mutandis, the same is true of coital ululations.
But underneath all this it's probably the neighbors being jealous of someone who clearly has a rich and satisfying sex life, unlike their own prematurely withered libidos.