Though in that one scene where the mother told the FL that she became like her dead sister when dating her boyfriend at the time, rather than saying it's because the FL dates the same guy I'd say it's because the FL unconciously tried to be just like her late sister because she loved her so much. I mean that's the only reason why it would make sense to become EXACTLY like the sister. Otherwise you couldn't become EXACTLY like the ex just because you date the same person, maybe similar but not exactly the same.
Now this was an amazing story!
Though in that one scene where the mother told the FL that she became like her dead sister when dating her boyfriend at the time, rather than saying it's because the FL dates the same guy I'd say it's because the FL unconciously tried to be just like her late sister because she loved her so much. I mean that's the only reason why it would make sense to become EXACTLY like the sister. Otherwise you couldn't become EXACTLY like the ex just because you date the same person, maybe similar but not exactly the same.