Hostel isn't based on any true events. It's a product of the filmmaker's imagination and designed to entertain with its horror elements and plot twists.
Beth Thomas in the story is a girl who had experienced early childhood abuse. She was then adopted and became known for her very difficult and disturbing behaviors such as harming animals and being overly aggressive towards people.
Yes, I once stayed in a hostel where the room was freezing cold at night. The heater wasn't working, and when I asked the staff about it, they just said there was nothing they could do. It was so uncomfortable that I barely got any sleep that night.