Her taking a picture and posting it to Twitter (which is different from publishing) is not illegal. She didn't need a model release. The only time you need a model release is if you intend to sell the photograph of a person to be used for commercial purposes. You know, sell the picture to a company for the company to use it in an advertisement. At that time, a model release is required. No monetary gain was acquired in this situation, so why would a release be required?
Know Copyright and publishing laws when you comment... just sayin'