Sadly, that is the entire problem, her new face. It kind of ruined her for me, and she was my favorite. Her old faces were great, now she looks like everyone else. No longer is she a unique flower, now she is just another dandelion.
If you tried to trigger Jenny's scene, before doing Debbie's arc passed a certain point, the diary will not trigger. You need to load a save from before you started Jenny's story, and finish Debbie's first, then you can go back to do that.
You will then just need to talk to her while she is lying on her bed at the time, and tell her that Debbie is looking for her. You will see her reading/writing in it when you enter the room.