Where do you think Arya's plotline is going?

So far I have been really liking season 6, and how a lot of storylines seem to come together. Most notably in the North, where a lot of different characters are finally meeting up: Sansa/Jon/Bolton/Brienne/Wildlings, even Rickon (RIP shaggy) are meeting up and interacting. Other storylines are still isolated, but there is a potential for later collision. For example the Iron Islands, it seems likely that Asha/Yara will fill the role of Victarion and sail towards Mereen.

However, one storyline seems very isolated to me, and I have no idea where it can possibly go, and that is Arya's storyline. She has been spending the last 13 episodes being in training with the Faceless Men, but what is she training towards? The only answer seems to be that she is going to finish her kill list, but considering that the people on her list are all very hated, with lots of people willing to kill them, it would not feel like a satisfying story to me. Why would Arya suddenly drop into KL to kill Ser UnGregor when there are so many other people in KL that would want to kill him?

Any thoughts on this?