Whoever is on the deed must agree to the sale. So, NO she can't sell the house. This should be addressed in their divorce settlement. It will either be awarded to one of them or be split 50/50 and must either be sold with each getting half of the proceeds or one spouse must buy the other out of his or her half. If they are both on the loan, they are both financially responsible. If he refuses to pay his half of the mortgage, when they settle, she may get more than half as she paid in more than half. If the home gets foreclosed on, it will also ruin HIS credit.
Until they get the divorce settled, I suggest she call her mortgage company to see what they can work out. I also suggest she start keeping a journal of all these spiteful actions as it will only work in her defense on judgment day. Get her name off the credit cards NOW!!!