I see nothing that would lead me to believe she was his girlfriend. They were ex-co-workers who knew each other. Am I missing something? Why would you think they were boyfriend and girlfriend? You could be doing a serious disservice to this girls memory by assuming she would go out with a rapist.
"Police say Ledet and Cooper were former co-workers and had a relationship of some kind but would not elaborate. They say Ledet was likely at Cooper's apartment since Friday or Saturday and that there was no sign of forced entry. "