It honestly feels like it's moved faster than it has in the book. I don't know if that's accurate, but she hasn't even been in every episode and has only had 1 or 2 scenes in the episodes she has been in, so by necessity every scene progresses it a bit further. It's done a great job of conveying the mystery of the situation and we are learning bits and pieces along with Arya.
The sequence of events foxtrot laid out just seems like it would take up drastically more screentime that the show just logistically doesn't have the space for. Not to mention the inclusion of multiple traditional montages (literal training montages even!), something I can't recall the show ever doing.
They have all been extremely well shot, well written, well performed scenes. They may not be exactly lifted out of the books, but it seems extreme hyperbole to say they've "screwed up" the storyline or it's been "poorly handled," or to suggest that the execution of the Arya storyline is representative of the filmmakers being "hacks." There's very little I can see to complain about with her story this season, because at the very least it's been completely competently presented, unless your complaint is simply that it's too different from the books.
I agree, and I reserve judgement of Arya's storyline until the last episode. It bothers me that they introduced the insurance guy AND sent Meryn Trant her way too. Will she kill both? Just one? None?