I think the only way she would have gotten in car with him was 1) she knew him at least tangentially or they had mutual friends; 2) he held up a weapon (unlikely bc she could have run); 3) she called an uber driver and she mistakenly thought he was the driver (have they ruled out any her calling for any ride share service?) or she was going to call uber and he told her, 'hey i'm an uber driver, no need to call - I will put you in the system right now' and because of his university id she felt it was ok; 4) he held up a police badge and maid up something to her about her breaking the law or whatever; 5) he said something to her that really appeared non-threatening, like maybe asked for help.