I'm pretty sure this is a very clever troll but as somebody who has just been through a bitter divorce I have to chime in anyway.
If he doesn't protect the money she will take every bit of it. He will have no way to recover. My ex tried to empty my personal accounts (which she did not have any legal right to do and the bank stopped her, barely) as well as our joint accounts. If she has moved out, it is GO TIME. Abandonment is hard to prove, depending on your state statute. Even if you end up keeping the house you will have to pay out any shared equity. Who knows, if you lost equity she may even have to pay you for you to keep the house, that would be sweet indeed.
If she truly wants to make things better don't flush your marriage down the drain without trying. But for God's sake don't let her move back into the house or have access to the cash.