I just tead a comment that took the dream to mean she preferred Gregory and would leave Phikip soon. Obviously I think that's silly but it made me think how after Philip has always been the one more in love this last ep gave all tge romantic gestures to Elizabeth.

She takes the rings. She tosses her old ring and gives him his (love that this isn't a reveal for him as if he's surprised she did it). She imagines an alternate life where they were fated to meet and fall in love as themselves without the work. Gregory is in the dream not as a rejection of himself but as a symbol of her earlier doubts about the kids. The fact that he's so nonthreatening as a rival in the dream really solidifies her feelings now.