If she had thought about buying a small amount of cannabis then I'm sure it would have been on offer.
Yes, I had wondered about that, too.
Those friends knew exactly where in the park to look for her
That isn't necessarily true. If they indeed knew that she took a particular route, then yes they might start by searching along that route. Otherwise, they might just have searched all over until they found her.
I agree that her two friends seem to contradict each other with regard to how frequently she cut through the park.