Is it that hard?
To find a teenager to play a teenager? Main character is very pretty, but at many angles it was obvious she was in her mid to late 20s and at least a decade older than the character she was playing.
To make a movie that makes sense? Like what would be the motive for the main character to kill her friend? Oh yeah, there isn't one so of course the makes her a suspect despite the DNA that would be all over the place from the dude.
Check an alibi? Talk to any of the hundreds of people who would have seen her friend walk off with that guy or talk to the guy the main character was with.
Overall super stupid movie.