The 4 star review doesn't know what they're talking about. Jinx/powder's writing on this show has been absolutely excellent and her motivations are quite clear.
From episode 1, powder desperately tried to fit in with a group that hated her. She tried to make the "right" decision her whole life, yet always managed to make things worse. Which is both quite relatable, yet also heartbreaking. In episode 3, the one person who had always defended powder (her own sister), then abandoned her and told her every insecurity she had about herself was true. This caused her to go into a mental breakdown because she has none one in her life to turn to.
Then, of course, when silco shows her compassion (because he sees himself in her), it makes sense why she joins him.
And that is what I love about this show. Its all about the writing of the characters. Vi, Jinx and even Silco are all three dimensional characters and I have a fair amount of sympathy for all of them.
Now, with that rant aside, this was truly another excellent episode, with that amazing fight with Vi at the end. I absolutely love the relationship between silco and Jinx. He seems to care for her, rather than just using her to get what he wants. It helps with my point about silco being an interesting character. I love it! The "being reborn" scene really captures this. I can't wait to watch episode 6. These arcs feel like entire seasons or movies in their own right!