Sounds to me like they were enforcing a law that's currently on the books which makes marijuana illegal.
SHE broke the law, SHE had the dope- why the holy fuck are the cops the bad guys here?
I've never seen much wrong with marijuana, and yep, it probably should be legal and regulated, because it's no more damaging, impairing, or problematic than alcohol. BUT- it's currently illegal, and if you're going to drive around with it in your car, then hey... you're rolling the dice.
It's like any other law you break, from speeding to murder- if you're going to break that law, don't bitch and whine when you get caught for it.
H