Rabia's theory: "Hae, who was dressed up very nicely because she'd be seeing Don that evening, was going to pick up some weed and ended up running into someone very dangerous."

To me, this makes much more logical sense than thinking that Adnan, who has never been violent, has a new girlfriend, success in a good school, would for some reason need to kill his old girlfriend, squeezing it in between end of school and track practice. I mean, c'mon.

It is far easier to put the pieces of the puzzle together if you start with:

Hae ran into someone dangerous, someone who also knew Jay.

Things start to fit together and make sense...