In my mind this is the hinge or the crux of the issue. If it was her job to create and inject JavaScript notifications of company policy and they fired her for doing that then shame on Google. Actually, it would be more than just shame on Google. If this is true, then I would say Google is not a safe place to work for anybody. Which is why I find it hard to believe that this was actually in her job description and or that there is more context that we are missing; that the premise of the argument is misleading.

"Part of my job was to write browser notifications so that my coworkers can be automatically notified of employee guidelines and company policies while they surf the web."

-With regard to what exactly? Context matters, if the browser notifications she was creating were only supposed to pertain to surfing the web then I think we can safely say she overstepped her bounds.

"So when I heard that Google had hired a union busting firm and started illegally retaliating against my coworkers, I decided to make sure that my coworkers knew about the posting."

-Again, it depends on what exactly her job was, but this seems to suggest she had motivation outside the bounds of her job description for doing what she did.

I don’t disagree with what she did. In fact, I think it’s kind of great. However, that doesn’t mean Google didn’t have a right to fire her for it.