Okay, so in the Great LotR-TMA Parallel List, right up there in the Biggest ones (along with ‘two men in either a romantic or a vaguely romantic relationship walk through a hellscape to an ever-watching tower with an addiction-related-MacGuffin that gets destroyed)* is:

Helen parallels to Gollum.

They both used to be people, maybe not good but not monstrous and evil. And they both have bits of the old self in; Helen is still Helen and not; Gollum still has a bit of his old self, even hundreds of years later.

They both serve as sort of…a reminder of ethics? Maybe 'what not to do’, but also 'should we do something about them?’ Martin, I think (confusingly enough) doesn’t want to smite Helen. (Correct me if I’m wrong.) Jon eventually does. Sam wants to kill Gollum, but Frodo does not, out of pity. ('Many who die deserve life. Can you give it to them?’)

The fact that Frodo does not kill Gollum is essential to the story. [SPOILERS] Frodo gives in to the Ring’s temptation right at the end, but Gollum bites it off his finger and falls into the lava with it. Now, I wonder if that means Helen would have done something at the top of the tower. Would she have wanted to do the Web’s plan? I suppose not. Same with Gollum and Frodo’s plan (throw the Ring in the volcano).

Both Helen and Gollum are absolutely essential to the plan, at its last, succeeding.

*Yes, this is, like, nine different distinct parallels.