Invisible Woman

This book is a waste of paper.

Spoilers, kinda, ahead, even though you kind of deduce this from the beginning.
I can go on and on about the plot holes (that thing that came up about Alex in the end felt like an afterthought and does not fit at all anywhere with the plot and how the characters dealt about it in the beginning), lack of nuance about feminism when it is a feminist book, lack of character consistency and development (which is embarrassing in such a character heavy book), lack of depth, the unlikability of the main character and the severe lack of understanding of how someone who has been manipulated and gaslit for 26 years would feel about sharing things with her abuser (which added to the unlikability of the character and made her sound well... dumb. At least in the scenes where basic survival instinct should have kicked in, like confronting the abuser of the crimes he committed, including attempting to murder someone, while being alone with them in the house? like telling him a secret she vowed to keep 20+ years before in relation to someone being raped (not her) and knowing because of earlier comments he made that at the very least, doesn't care about the topic at all). It felt like reading female characters written by a man who calls himself a feminist on twitter.
The writing style also felt forced? Like someone who is writing what they think their professor at university wants to read. The descriptions were very awkwardly put in the flow of the story and sometimes were irrelevant and made me frustrated and the inner monologue of Joni was annoying because it didn't even make sense at times. It felt patronizing a bit to read it as someone who did survive abuse very similar to Paul's, which is a type of abuse that is very common sadly. And the ending fell flat as literally everything was predictable but Joni's actions were not calculated, reckless, impulsive and dumb.

What was the point of the twist that one of Joni's daughters was dead, and that Joni was imagining her? Why was that in the book?