Forgive me if I'm missing something, but if another version of Gollum is in play, that would imply that
Gollum, Her Sneak is not in play, and as long as
Gollum, Her Sneak is not in play, its text isn't even active (since the text of
Gollum, Her Sneak gives no indication that it applies when not in play, e.g., when in your discard pile).
So, no, the text of one version of a unique character can never apply to other versions of that character (unless that text specifically indicates that that text is active while the card is not in play, e.g., "While this card is in your discard pile, Gollum is strength +2.").