I really liked this chapter, too!
Again, I felt like you revealed just enough detail about Josephine and her relationship with Fred to intrigue me more without leaving me feeling completely flat-footed. I'd been wondering whether she'd had feelings for Fred, but now the situation makes perfect sense. In some ways, I actually feel like the extent of her grief makes more sense now, because the impression that I'm getting is that he was really her only friend, and now she's in a position where she's essentially alone in the world. I'm curious about what happened to her family and why she doesn't have any other friends, but I'm willing to wait to find out, and it doesn't seem unrealistic to me, just sad.
I'd also been a little confused about how she could not know George if she was so close to Fred, but now that makes sense, too... and I'm starting to think that she probably felt closer to Fred than he did with her. Not that he didn't like her, but she seems very lonely and cut off from the world - the surprise she seemed to feel that George remembered that she'd been there after she ran off made my heart ache, and felt depressingly real. I'm definitely getting a strong sense of who she is as a person, and I really feel for her; this is a terrible situation to find yourself in.
Based on the story summary, it seems like there's going to be a fair amount of deception in this story, and I felt like you sort of foreshadowed that a little with the way she was watching George and Mrs. Weasley at the end of the chapter from behind a tree. It was very well done, and has me eager to read on.
All of that said, I did think that this chapter had the same issue that the last one did. It just got a little too wordy or included too many adjectives at times where I felt like less would have been more.
I felt like you often used dialogue tags or short descriptors where they weren't necessary, which impacted the flow of the chapter. For example, in the first sentence, I don't think you needed to say that Fred was whining - the way you wrote out her name already implies that. Similarly, when you say that he "brushes aside" her silence, or "chuckles in low vibrations," or that she gives "a silent laugh," I feel like you're not really adding to the story or the narrative in a meaningful way.
There are just a lot of points where it feels like you're just trying to break up the dialogue or add more description, but based on your writing as a whole, I think you could probably do it in a much more graceful way. Think about whether your descriptions are really helping the reader form a picture in their head of the scene or contributing to their understanding of Josephine and/or Fred. If they aren't, you probably don't need them.
I also felt like you did a little too much telling rather than showing about her feelings toward George. I loved the Dementor analogy, and I wanted to see a little more of it. What is it that she loves about George that Fred doesn't have? Does she daydream about him? Does she wish that he'd died instead of Fred - or, alternatively, is she relieved that it was Fred over him? Does she feel guilty about that?
Maybe you go more into this later, but I would have liked to see a little more now.
Overall, though, this was a great chapter. I thoroughly enjoyed it, and I'm excited to read on!