Actually, she didn't understand Phoebe Smith at all. If she had, she and Oscar Smith wouldn't have been so reckless. Perhaps then, she wouldn't have lost her precious life.
Jinna Evans and Oscar Smith were both unaware that not only was there no soundproofing in Jinna's room, but there was also a pinhole camera in the corner of the wall, which Phoebe Smith used to monitor Jinna's daily activities, afraid that Jinna would be up to no good behind her back.
Indeed, Jinna hadn't done anything behind Phoebe's back; she didn't have the guts to betray Phoebe. However, her every move with Oscar in bed was watched by Phoebe.
Trained in such arts, Jinna was no slouch in bed with Oscar, performing with all her might, thinking to please the big boss so Phoebe wouldn't dare boss her around later.
What she desired even more was to bear Oscar's child, thinking that once she gave birth to Oscar's child, Phoebe would have to respect her and wouldn't dare order her around anymore.