Pretty Ugly People (2008)

Former college chums gather for what they think is their fat friend's dying last days, but they instead find her celebrating the last few days before reaching her target weight loss at a mountain lodge with a subsequent hiking trip planned for them all. Though it's the woman's long-held dream journey that she wanted to take with her best friends, the others, largely, can't get over the feeling of being duped, with everyone's emotional baggage breaking out awkwardly all along their forced and uncomfortable three-day hike back to civilization.