How does the atmosphere in Sammie's home change after the break-up with Monika in the novel, With Teeth?

The atmosphere of Sammie and Monika's home changes drastically after they split up. Although they have broken up, neither Sammie nor Monika moves out of the house. Instead, Monika takes up residence in the guest room, which has "its own bathroom, with a giant walk-in shower in lieu of a bathtub" (214). Meanwhile, Sammie continues to claim the master bedroom as her own. Because of this new arrangement, Sammie only feels comfortable in the house when she is there alone on weekday afternoons. Not long after she spends one such afternoon snooping through Monika's and Samson's rooms, Sammie learns that Megan will soon move into the house, too. This revelation is Sammie's cue to move out and start a new life.