Caporegime
You don't need a montage You just need bits here and there. And no, I don't think her limited sword training with Syrio and then the assassin training in Braavos is in the same realm as that sort of sword fighting. We've not seen her do anything like that before or train for anything like that.@Vonhelmet - I don't know how you can say that we haven't established Arya is a bad ass... she went through loads of training, was sword trained in the first series, fought with the staff whilst being trained, killed someone in the pitch black (i.e blind), has killed loads of people... it's obvious she has the skills... and even then she didn't beat Bren so it's not like she's 'overpowered'.
Would it really be necessary to show only more than what we have seen? I think you've set yourself up to be annoyed if that bothered you. I viewed it as Arya demonstrating how skilled she is - was that not the whole point of the scene? Would you prefer a Rocky IV montage?