I can speak for the U.S. since I work in HR here. It's not likely she'll get fired for this unless there's some other mitigating circumstances we're not being made aware of in this post. It can also depend on where they work and that place's culture - an office job in a halfway decent company will almost certainly not fire her. I also doubt a retail job, warehouse position, or any other blue collar job I can come up with off the top of my head would fire her for being 'transphobic' either. Essentially what happened here is a bad ending to a workplace romance*, and unless she works in a crazy liberal city for a 'progressive' company her chances of termination are very small.

The fact that she thinks she'll be able to get her co-worker fired is what's truly crazy to me.

*This is how HR will look at it; on a personal level I find it beyond loathsome.