jokes aside, we know it was Bella's parents house and looking at the layout, left door is Bella's bedroom, middle is bathroom, 3rd door should be another bedroom, that leaves several options
1. After Bella's parents died she moved to their bedroom, the right door was her childhood room, then converted to a baby room, baby dies, room stays as a shrine, depending on how long ago it happened, mildly creepy
2. Bella moves to her parents bedroom, her room remains untouched as she left it, she killed small animals as a kid
3. Bella stayed in her room, right door was her parents bedroom, they didn't die in a crash but are mummified in bed
4. Bella had a child when she was 15, it's Sage, Morgan is the dad's name, the room is covered in Sage pictures because Bella has stalked her her entire life including getting a job at B&R
5. James was a doomsday prepper and converted Bella's room in to an armory, its full of guns, lots of guns