I think those phone records take some time to get. Trying to remember from a previous case I followed. Maybe it was MT. They took maybe 10 days.
Getting the phone numbers she communicated with, call durations, etc. is really quick for LE. That info is already tracked on a the monthly bill so there is no legwork to do, just a question of whether or not access is necessary. Plus, her bill was likely in her parent's name if she had a cell phone. Getting the phone bill of a homicide victim would be really fast. It could take less than a day.