That's a useless analogy on several levels!
1) If she was posting from her work PC, they'd have had every right to do so.
2) If not, let's see their employment contract and see the wording that forbids posting to such a website using your home PC on your own time.
3) Finally, the Anti-Christian Litigation Unit (ACLU) wouldn't care if anyone got fired for that reason. Some speech is just more equal than others.
I was thinking your #2 when I posted. I should be more clear. Sorry.