Lavender receives a letter informing her that her young pet rabbit, Binky, has been killed by a fox. She takes this upsetting news as evidence of Professor Trelawney’s powers of prediction, but Hermione tries to point out why that is a flawed conclusion (PA8).
Lavender believes the receipt of this news (on the sixteenth of October) is the fulfillment of Trelanwey’s prediction “That thing you’re dreading, it will happen on the sixteenth of October” (PA6, PA8). Lavender is in tears about it all just before Transfiguration when Hermione points out that 1) Lavender couldn’t have been dreading that Binky would die since his death comes as a complete surprise to her and 2) the sixteenth was merely the day Lavender learned of Binky’s death, not the day he actually died (PA8).
Ron, who is still upset about Crookshanks and Scabbers, loudly consoles Lavender with the comment that Hermione “doesn’t think other people’s pets matter very much” (PA8).
Ron's behavior here - aggravating Hermione with his attention to Lavender - seems to foreshadow some of their sixth-year drama. -BB