I guess what I'm asking now is.. What do I do when W approaches me in public or at D30 house and starts asking me questions?
D30 is planning on moving in with me when I buy a house in 5 months so she can save money. It was her idea and I like being around family now that they are my priority.
Im not sure I understand your question.
Id treat her like you would a neighbor that youre slightly acquainted with. Short of friends but north of someone you despise. Like a coworker.
If she starts to go deeper, just say you dont want to discuss XYZ at the moment.