Board Thread:False Info and Speculative Discussion/@comment-24.130.28.230-20150721180826/@comment-4091815-20160131170022

She inherited her ability from her grandmother. The trauma of the bite and the mental difficult that followed did bring that innate ability to the fore, but she always had it.

In addition to Lydia, we know that all Banshee seen on the show have crossed and/or used Mountain Ash with no difficulty.