Actually, probably not. In a case like this, it is the church (employer) who gets to define the term, not the employee. As long as the school can show that the Bible teaches against such behavior (which it does), then they can support the firing.
It’s not about her, it’s about what’s best for the students...period!
The Bible also teaches against divorce yet they hired her anyway. From a legal standpoint even terms based on Bible teachings must be spelled out to avoid any confusion.
She is likely to prevail.