How to respond to a ridiculous lady at work sending out warning emails about fake terrorist stuff?

Today this lady at my work forwarded an email of a former coworker's sister's cousin who works at UPS and said that terrorists are buying UPS uniforms. I promptly searched this on google and it immediately told me this was a hoax dating back to 2003. The department of homeland security website even had the same email word for word on their hoax website. I politely emailed the woman back saying it was a hoax but who knows these days with all the craziness in the world. I sent her two links about it being a hoax. I find it very unnecessary for her to email people and potentially scare them when it's unwarranted. Later she comes up to me and snottily defends her email because it's from a "reliable" source. The email was WORD FOR WORD from the DHS website that said it was a hoax. Should I have laughed in her face? She was so rude and it was sooooooo ridiculous. I just said ok and left it at that. Why are people so gullible and so damn defensive. Or did she just feel like a moron and had to defend her ridiculous company-wide email?