Is this someone with dreadfully crass taste in t-shirts, or is she actually just trying to look out for the people close to her? There's nothing worse than being caught downwind of someone who's just passed gas, and it's even more foul when you're trapped in an enclosed space with them. Sometimes, you wonder why people can't just walk a safe distance away from anybody else before they let one rip. A warning would be nice.
Anyone walking too close to this woman can't say that they didn't get a heads up when the inevitable happens. Farts happen to all of us whether we want them to or not, and it can be embarrassing both for us and the people who can smell them when they do. Maybe we should all take a leaf out of her book, and show a little more consideration so people can get out of nose range.