Yeah, not entirely sure why they went with a complete name change for her. She was clearly supposed to replace Jeyne Westerling, unless this was another one of those instances where they didn't want to confuse character names with Jeyne Poole. IIRC, Poole was present briefly in season 1 prior to the fall of the Starks at Kings Landing but never seen again - a thoroughly minor and forgettable character to be sure. They can pick any other minor female character to be "fake Arya" later on, sent up to be Ramsay Snow/Bolton's bride and nobody would know any different. If anyone should have had a name change, it should have been her, not Westerling.