When she had finally taken a step back, and looked at the things that were going on in her life, especially when it came to her job, Emily had realized something .
She and Derek were in a professional situationship. If the two of them had been romantically involved, the whole thing would have played out something like this: She had ended things unexpectedly and then Derek had pretended to be all tough and accept it. Then the moment that he had realized that she was really gone, he had broken down in tears and had decided that he was not letting her go. Which was why he was suddenly making things so difficult for her. Meanwhile Emily, after ending the relationship, regretted it and wanted to go back, but could not because her faults would ruin what they'd had in the past.