Totally agree with Maria D, if we heeded every warning about what was bad for us we would barely breathe let alone eat and drink!
It is possible that something in the Diet pop that person was drinking aggravated a condition she may already have had so cutting it out would obviously reduce the symptoms. As for the Aspartame causing these symptoms, I'm not so sure that it's anything more than scare mongering. In Britain the government are quite hyperactive when it comes to good food/bad food and if any of this had scientific or medical standing then we would have heard something more than an anonymous story from the States.