How does foxface die??

Foxface died from eating the nightlock that Peeta left on the plastic sheet while Katniss went to go hunting.

Foxface ate some deadly berries that Peeta had collected. He dropped a few and she sneakily ate some and died...

she attempts to steal some food from peeta but the food she steals ends up being the poisonous berries that he collected.

When Peeta was collecting berries, he accidentally collected poisonous berries and left them on a tarp. Sense foxface relied on other tributes for food, she supposed the berries Peeta picked were safe to eat. So, she ate them and, because they were poisonous, she died. Instantly.

foxface in the book died after thresh but in the movie before and she died because peata had poisinis berries (he didnt think where poisenes) on his jacket so foxface thought they where ok so she ate them and died