I think the reason she dreamed about her ex, with his girlfriend is that there is an unclosed connection between her ex. The invitation of his friend from the bus stop to his house represents her wanting to move on or just to make her attention pointing to something else to avoid thinking about him. The things she left behind was her actual feeling for his ex, and try finding it means that she still hopes everything will go back to the way it was. The room where she thought was a computer room but got into a hospital instead represents her feelings, hidden and hurting from her past relationship and the fear of catching peoples illness is the fear of loving and trusting again.