So in the Lorien Post I explained the elves waking up and being called to Valinor to dwell with the Valar. I mentioned that some made the Journey and some did not.
After the elves arrived in Valinor and were living under the Two Trees (Explained in Part I and Part II ) their elven lives continued ...meaning they had children. One of those children was Galadriel and another was Fëanor.
So how then did Galadriel get back to Lorien if she had already been to Valinor? Why would she go back? She wasn't the only one is the simple answer. The more difficult answer is Melkor.
Melkor aka Morgoth aka the Dark Lord (first one) aka Sauron's master. And incidentally the creator of Balrogs hence Balrog of Morgoth. While he was a god he was already chained up for having destroyed the Lamps of the Valar and basically ruining everything.....that jerk. When the elves awoke the other Valar judged him to be dangerous to the Eldar (elves) and so they stormed his fortress in middle earth and took him in chains back to Valinor.
The Elves made it to Valinor and then Galadriel and Fëanor among others were born. Fëanor was said to burn with a fiery spirit. His strength was so great that upon birth his mother's spirit passed into the halls of waiting (she died). Fëanor would become the greatest crafter of the Eldar. Learning his craft from another Elf named Mahtan who studied with Aule (the Valar often called the smith).
Fëanor was such a gifted crafter that he created gems and jewels. He made lamps that glowed by themselves and the very well known palantíri. What is that? They were orbs that could see over vast distances. Perhaps you will remember in the movie Sauruman is using one in his tower and Gandalf warns him of the danger because no one knows where the other palantíri are. Anyway I am getting sidetracked.
Fëanor I believe had a deep rooted desire to create something like the two trees. Mostly because Fëanor had asked Galadriel for a lock of her hair once. Galadriel's hair was said to glow like the two trees. She refused and the two of them never really got along. I think Galadriel had a thing for him but that was never said. Just my opinion. Anyway so Fëanor set about to use his crafted Jewels to capture the light of the two trees. And he did it. They were called Silmarils.
As it turned out those Silmarils caused tons of trouble and not much else. Melkor desired them and in fact stole them after destroying the two trees. Its interesting to me that the Valar freed Melkor believing him to be changed. Anyway Melkor destroys the two trees and steals the Silmarils. According to the Valar the only way to heal the trees is using the light inside the Silmarils. Feeding into Fëanor's belief that everyone was after the Silmarils. He is a bit paranoid about them.
Fëanor is so enraged that he creates an oath to which his sons swear with him that they will get the Silmarils back no matter who tries to keep them from them. Even if that means fighting elves or even Valar.
Fëanor by making this oath utterly screws up elves for all time. He goes to the Teleri and asks them for their ships to pursue Melkor/Morgoth across to middle earth. They refuse and so Fëanor and his troops take up arms against the other elves to take the ships by force. Its here the first slaying of elves by elves takes place.
After this some of the elves turn back and are forgiven by the Valar. But Fëanor and his sons and loyal elves were now driven by the Oath. They burned the boats leaving many elves stranded wanting to follow but not being able. I believe Galadriel was in that group. She and the others crossed the Helcaraxë lead by Fingolfin. The Valar warned them all not to pursue Morgoth.....but they did it anyway.
So the elves came to be in middle earth again having once been in Valinor. Years of war against Morgoth and among themselves over the Silmaril that was recovered. And then again when Morgoth was taken away by the Valar in the War of Wrath...the two remaining brothers stole the two Silmarils. Both of those were lost as well.
So all that played a part in the oath of Fëanor and the returning to Middle Earth against the Valar's wishes were Banned from returning to Valinor. To us this singles out Galadriel. Who although did not take part in anything besides crossing the Helcaraxë against the Valar's wishes was still prevented from returning.
That is until she turned down the One Ring when Frodo Offered it to her. This act absolved her and she was allowed to cross into the west to the land of her birth. Its important to note here that aside from Círdan the Shipwright in the Grey Havens Galadriel is the oldest Elf we know of still in middle earth at the end of the Third age.