In the first place, there's absolutely no reason at all to imagine that these two alternatives are the only possible ways a mythical character might have come about.

Outside mythical and extremely fictionalised sources, there's no actual evidence to corroborate the existence of such an individual, or indeed of anyone involved in the Trojan War legend (see further the Trojan War section of our FAQ). Absence of evidence isn't evidence of absence, of course, so that doesn't exactly prove that she didn't exist, but the majority of dateable features of Greek social practices and material culture that we see in early mythical texts points to the eighth and seventh centuries BCE as the basis for the imagined setting: in that context, it would be a big leap to select one specific individual and suppose that she was an accurate representation of a Bronze Age historical figure.

So that's a big no to the first alternative.

There's no reason even to engage with the second alternative. If mortals in Greek legend had a track record of being personifications of something or other, there might be some reason to go into it. But they don't, so it's blue sky speculation.

So that's a big no to the second alternative.

(Having said that, some specific literary writers certainly reinterpreted mythical figures symbolically or allegorically and superimposed their own symbolism on a pre-existing legend. In Aischylos' play Agamemnon (458 BCE), for example, there's a fair amount of wordplay on the names "Apollo" and "Helen", and their resemblance to certain words for destruction (apoll- = "destroy", hel- = "capture, overthrow"). But that's certainly not the real etymology of either name: it's a case of re-imagining the myths after the fact. Homer does the same with some names -- though not Helen.)

It's impossible to say. There might well have been an historical Helen over whom a war was fought, but there is no independent confirmation of the specific events of the Iliad. Archaeologists are pretty confident they have located the historical city of Troy, but it's a long step from that to the existence of Achilles, Hector, Paris, and the rest. All we have is Homer's story.

Herodotus claimed that the Persians claimed that the entire conflict between East and West (leading to the Persian Wars) started with the carrying off of women. Various people of Asia did it. The Greeks did it to them (Medea). And then when the Trojans took Helen the Greeks completely overreacted, like fools, and led an army into Asia. Therefore, all conflict starts with them.

"Now as for the carrying off of women, it is the deed, they say, of a rogue: but to make a stir about such as are carried off, argues a man a fool."

If Herodotus said it then it must be true! Helen was real.

No, I am kidding. (And, he just said it was a claim he didn't say it was true.) Given the geography of Greece and the fact much of it is on a coast it is likely that women were abducted on occasion. So, it isn't absurd to think that some abductions worked their way into the imagination of the people (there are several stories of women being abducted and Odysseus makes a big production of letting Nausikaa know he has no intention of raping or abducting her). So, I think there is reason to believe this is a thing that happened.

But there is no reason to think there was such a woman as Helen or a war was fought over the abduction of any woman. And Herodotus himself points out that it is just plain absurd to think a whole war would be fought over the abduction of a woman or, if that did happen, that Troy wouldn't just immediately give her back.

I think the idea that it became part of the story because of some remembered abductions is not unlikely. I don't think she personifies the land. I am not sure that works. Since she was abducted that would suggest a Trojan capturing of the land? What exactly would she personify?