Everyone here seems to think the in-laws were just the loveliest people ever-- and they may well have been. But I totally sympathize with Bethany in not wanting them to practically move in together. Given her background and her lack of any independent relationship with them-- and her independent loner spirit-- it's understandable that she found this enforced closeness invasive and unwelcome. And the constant condemnations from Jason in combination with her self guilt-tripping neuroticism, must have made it intolerable.
She seems to be an incredibly needy person to me, but she had a right for her voice to be heard in the relationship with the grandparents-- and I don
't think that was happening.