Stop covering for her. If you wish to get involved but want to maintain a safe distance from the fallout take a few shots of her escapades and have it sent to her husband when you know she isn't around. Anonymously. And I don't think she turned into a greedy, selfish individual overnight. She's always been that way and has been successful (until now) covering her tracks. You owe her nothing and she isn't a friend since she's put you in this position.