Other mistake: Just after Grandma Willow says "There's still some snap in these old vines," John Smith puts on his bag, but he just presses it to him instead of putting it over his head.
Other mistake: When Percy sees Meeko in the bubble, it is done in first person perspective and we can see straight through the bubble, showing that Meeko is not there on the other side.
Answer: She didn't exactly hate Kocoum though. She loved John, sure, but Kocoum was someone she'd known her whole life. It's not unreasonable she'd be upset over his death, whatever the circumstances.
Phixius ★