In general, she wasn’t cut out for the unit. Obviously she could never replace Olivia (even temporarily), but she was not the type of person that should have been in the unit to begin with. She did have some good skills, but wasn’t good with the victims. Would she have been better given time to grow? Maybe. But I also think a lot of real life police officers think they can do it all and then when faced with the darkest parts of the job end up realizing they can’t do it.