If they already believe you committed the crime... Might as well do it. Let the fart free man, it wants to be free.
The rumbling might have to do with holding it in actually. Find an empty hallway to crop dust like a villain then immediately evacuate the area, fart near some ones cubicle you don't like, (such as a certain female co-worker you recently had issue with) or just go to the bathroom.
Also, they probably have trouble with this particular person often. I doubt it's just you she takes her stress out on. She's probably already complaining about the person she's been moved next to.
Yeah, well, you know, that's just, like, your opinion, man.