Can someone levy my wifes account?

Your ex-girlfriend must have got it done with the help of her attorney. You need to speak with your attorney and prepare your case.

Did you check with the local court if there is any case against you? Sometimes, fake legal papers are issued if it helps to recover your money faster. This kind of thing is illegal and you can take actions against the other party. Check the latest credit copy to confirm about this judgment.

No, as you've explained it, this was not legal. I assume you were not married when this "debt" was incurred. With a judgement, your ex-girlfriend can garnish you, but not your spouse (she isn't a party to the supposed suit, is she?), and generally speaking, joint property/accounts should be safe. I recommend getting an attorney promptly.

Did you know you were being sued? If not, was the proof of service properly executed? Like mute805 said, check with the appropriate court.