My wife was terminated and the explanation she received was that this was her second sexual discrimination write up. She had been written up once before for an incident. She was terminated and was not told what the offense was, only that this was her second offense. The corporation said that they confirmed this offense with others in the office. She has no idea what the offense is.

Is it legal for this company to fire her without telling her exactly what the sexual discrimination offense was?

Yes, it is. They didn't even have to tell her what they did tell her; all they had to do was say, Jane, your services are no longer required.