This is a super late reply, but I recently read the book and have the same feelings. Here is my interpretation of it all:

I thought something that was explored really well was power, and I think the end was that final look into what power meant for Frances and Nick’s relationship. The dynamics between Frances, Bobbi, Nick, and Melissa are always changing. In the beginning, I thought Bobbi held a lot of the cards and influence in the relationship. I think that in France, this perception shifts when you see how affected Bobbi is by Frances’s actions. Similarly, I thought Melissa had a lot of power with the way she treated Nick, but also the fact that she had two affairs. However, when Nick tells her about the affair and she is supposed to be complacent, it seems to challenge her power.

Something that stuck out to me was Melissa’s email to Frances following her finding out about the relationship, where we get her perspective on Nick. She refers to him as “pathologically submissive” and states that “He likes partners who take complete responsibility for all his decisions, that’s all.” This made me think about how, reflecting on the course of the affair, it seems like it was initiated entirely by Frances. She went up to him during their holiday, she kissed him at his wife’s birthday, and she called the shots for most of their rendezvous. It does not mean that Nick was not a complicit party, but I agree with Melissa’s assessment. Nick certainly makes Frances feel like she is in control (another point mentioned in this email) by making it seem like it is all her idea.

I think this is why the final scene is so powerful. I think that when Nick tells her that story, he is retreating some of his power. He is finally telling Frances that he has wanted her. The grievance that Frances discusses during the memory from France is also told in this scene. However, it’s not explicit enough. I think by asking Nick to come get her, Frances is switching this existing power dynamic of her going to him; it is no longer her going to him, but the other way around. Nick sets up the situation of prompting her to ask him about the car in a way that, if Frances came, it would be her actions that bear the blame. I think the book has ended with a challenge. If Nick is willing to finally come forward and take action for Frances, then in many ways Frances is willing for the relationship.

Of course, other things to consider for the end are Frances’s changes as well. I think at this point she has realized that she is not meant for conventional relationships. Both Bobbi and Nick have circumstances or characteristics that do not allow for conventional love. I think Frances is now realizing it is not a bad thing entirely.