Arya had to be the one to pull it off. She had been broken down psychologically and physically over the course of years and built back up to be a cold-blooded assassin. She was constantly put in a box and playfully overlooked by her older brothers. Jon was one of the few who really admired and encouraged her fighting spirit. She is probably the most skilled fighter in Westeros at this point. I think she may kill Cersei in the next battle, but it won’t be easy.