I do not see anything in the links posted on writing about fiction that support the lead being just "Faith".  The name of the character is "Faith Lehane" (defined by the franchise), and the article's first sentence should start that way.  The fact that the characters surname was only created/revealed later than the character's first appearance is notable and of course should be described later in the article, but that does not change that the article should start by describing the current version of the character. —(T•C)