First of all, you're entirely wrong that an employer can't yell at you for calling in sick. Secondly, just exactly where are you reading that he was yelling at her because she called in sick?
I'd be very interested in seeing a link to any site either rjjamison or Jeff-Hulk-Hemp would care to post, which shows a law saying a boss can't yell at you for any reason that's been posted on this thread.
Taking adverse action against someone, maybe. Yelling at you; sorry, that's legal.