By treating her differently you are actually making her more of an outsider. She should be treated how she needs to be treated, like a DIL. You are doing no one any favours by allowing her to continue living like she’s part time married. Wants and needs are very subject, one should always aim to treat someone how they NEED to be treated rather than how they want to be treated. Everyone wants to be treated like the Queen of Sheeba but no one needs to be treated like that.