During a telehealth session, a 32-year-old single woman reports being home during the quarantine for a period of 4 months with no outside contact. She says she knows several people who died from COVID-19, and although she never became ill, she has become extremely nervous about leaving her house. She tried leaving her house once during the Phase 1 reopening, but she says it felt like "an elephant" was sitting on her chest and went back home. She is terrified to use public transportation or go to any stores and stand in line, in case she has another episode of chest pain and "cannot escape." She is too terrified to go out again but misses seeing her friends and family. Which diagnosis is most correct?