[@DearTrickster] The conditions of her all of her magical contracts are known only to her, Puck (Robin Goodfellow), and the client, but Puck holds the contract and knows it better than others involved, so he's well aware of loopholes. Marie, having worked for him for the better part of a year, would also know of a few loopholes, so if a magical contract isn't worded specifically or doesn't take into account previous/subsequent acts, then it can basically be voided by the involved parties if they are aware of this. 

All of this basically means that if the contract that binds Marie to the villain's service doesn't specify that she can't interfere after the contract is complete, then she can do what she wants. She's also able to lie about he moral character while under contract so as to avoid suspicion.