Sometimes people do stupid things and this is one of them. But if you look at the bigger picture, her debt is also his since they are a couple/married. Debt is gone so that's a good thing, right? She didn't use the money for gambling, or something else...
AND no, she's not an opportunist but rather made a poor decision. Don't we all made poor decisions from time to time? Even among couples... This is why people work thru things and do better.