Can my wife be fired for comments made on my personal facebook profile.

My wife was fired after I posted on Facebook about her employer demoting her for no reason that was written or verbally stated. She was terminated because of a contract that she signed stating she wouldn't speak ill of her employer on FB. In that contract it also states relatives may not either. I had no knowledge of this until after her termination. Is that contract void because I myself did not sign a written contract stating I wouldn't speak ill of her employer? Do I have the first amendment on my side or is this something we have to deal with?