She approached to ask for permission. If they had any reservations, that was the time to discuss them. She did what was expected of an employee. The fact that they blessed her and then went back on their word seems wrong.
Not a lawyer but my intuition says there might be some legal grounds here favouring the wife.
My take is someone even higher up found out later and did not like it. Now it’s entirely possible the individuals who gave their blessings were supportive of the party the wife was standing for, and the ones above them weren’t? Still whoever blessed the campaign did so in their capacity as a senior officer of the company. A total shit show nevertheless.
To the original commenter: sorry this happened to your wife. Hope she’s able to find another job that treats her right. Also congrats on the baby, hoping parenthood makes up for all of this and more. Sending the best of wishes your way.