The whole movie is about how Frances is kind of drifting away from Sophie like so many friends do in the process of ‘growing up’ as their lives change and pull them into different directions. I love this moment, right after Sophie and Frances share this intimate moment the night before in Frances’ dorm, where Sophie and her fiance are driving away. Sophie chooses to move on with her new life. Frances finally kind of comes to terms with it when she watches them go. She kind of comes into herself there.
Then, at the end of the film, we see Frances making her own new life for herself without Sophie. And despite their two independent lives they have this moment, the moment that Frances has always been searching for, where their eyes meet from across the room and they just feel this bond that only they share and will always share.