Her return is 'obligated' because it's her fate and an essential path of her life as a royal High Elf from Valinor, who witnessed the Splendour of the Two Trees.
The initial Perfection of the World was inevitably marred and corrupted by the powers of Melkor/Morgoth, who used Arda (except obviously Aman) as his own personal One Ring to spread his will and evil essence; and condemned it to an ineluctable destiny of decay and corruption, something that the Three Rings momentarily slowed and stopped.
The fate of the Elves was thus already decided (even before their Awakening in Arda), and that's why the Valar wisely decided to invite the Eldar to Valinor and always persuaded to sail towards it or return; because Valinor is the only place in which the Elves can live fully according to their nature of immortal beings, without fearing corruption or decay, since Valinor was made by Immortal Beings and made immortal by them.
Galadriel obviously knows this really well and her longing for the Undying Lands is always vivid, but she is divided and worried, because, as she tells Frodo in FOTR (book), the Love of the Eldar for their creations is deep as the depth of the Sea and she doesn't want to leave her realm and condemn it to vanish along the Ages of the World; but she is also well aware that, whether Sauron regains the One Ring or the One Ring is destroyed, her realm and her powers are doomed to fade forever and her people become rustic inhabitants of darkened woods.
That's why she also personally tells Frodo that she wishes that the One Ring had never been created, and thus letting the Three Rings to allow the Elves to stay in the World for other centuries without diminishing.
Her return to Aman is obligated by these facts, the sad story of corruption, decay and disenchantment of Arda, that goes from the initial titanic wars between the Valar and Melkor, to the betrayal of Sauron with the creation of the One Ring.
Here's another kicker though...
Wether or not the decision of the Valar to take the Elves to Aman was wise or right is actually a pretty hard question. Even the Valar weren't 100 % sure on this. Some (amongst which Ulmo was chief) thought that the Elves should have been left to wander Middle-earth and heal the land with their gifts/skill.
So the marring of Arda is not necessary the reason for the elves to retreat to Aman, but the reason for the elves to be (or stay) in Arda and enrich it with their subcreation.
This can also be seen in the fact that the elves were never quite "at home" in Valinor. Many of them stayed in Tol Eressëa, in between Valinor and Middle-earth; Most of them stayed in Eldamar, as close to Middle-earth as possible, and i think it is even stated somewhere that the Vanyar sometimes travelled to the shores near Alqualondë to at least gaze upon Middle-earth from time to time.
That's why there is definetly a connection between the elves and the "mortal lands".
I'm not sure if the disenchantment of Arda can be seen as that simple a reason for the elves to leave Middle-earth behind. It was a factor of course, but i think the desire for healing of whoes and wounds is as much a decisionpoint as well for most elves (though Galadriel is a special case of course).
Actually I have to correct you
Wether or not the decision of the Valar to take the Elves to Aman was wise or right is actually a pretty hard question. Even the Valar weren't 100 % sure on this. Some (amongst which Ulmo was chief) thought that the Elves should have been left to wander Middle-earth and heal the land with their gifts/skill.
So the marring of Arda is not necessary the reason for the elves to retreat to Aman, but the reason for the elves to be (or stay) in Arda and enrich it with their subcreation.
Yes, it's true, but this was mainly the opinion of Ulmo.
Manwë, Varda, Mandos, Nienna, Yavanna, Aulë and Tulkas had the opposite opinion though, because they cared so much for the Elves and they were afraid that they would have been in great danger among the still-present darkness and shadows of Melkor in the World, even though he had been previously defeated and brought in chains to Valinor; and they were right, since many Balrogs had hidden themselves, and Sauron were breeding legions of Orcs, to prepare the return of his master (and you should understand it, because you are a Vala yourself Adamin
).
Also, we shouldn't forget that Manwë is the dearest Vala to Ilúvatar (he is not the most powerful of the Valar, but he's definitely the wisest, and from it comes his absolute authority as the King of Arda), the one who understood better its Vision/Plan; and Manwë consulted with Ilúvatar in his own mind, before taking the fundamental decision of inviting the Elves to Aman.
The Elves have indeed the power to heal the wounds, or, better, they had it in the 'young ages' of their kindred, when the World was not so dark, and I didn't deny it, nor did I say that the Elves were immediately threatened and obliged to leave due to the sad fate of the World; it is a slow and long process of corruption and decay that it obviously shows itself manifestly only in the late Third Age, but it was anyway decided long before the Awakening of the Elves, and the World had already been 'cursed' by it.
This is the saddest aspect of all the matter.
Yes, Aman is not the motherland of the Elves, but it is the only land in which they can openly and eternally live according to their nature of immortal beings, really the best place they could have ever opted for.
Tolkien often stated it in the Silmarillion, the Eldar that reached Aman, or, better, the Eldar that were born there, blessed by the Holy Light of the Two Trees (like Galadriel and the Noldorin Royal Family), achieved immeasurable and immense levels of Splendour and Knowledge, surpassing all the other Elves ever born in Middle Earth; and we know that this Splendour and Knowledge then gradually passed (obviously at different grades) to the Noldor in Beleriand, to Númenor and, then, to Arnor/Gondor.
It's quite impossible thus that the Elves feel out of place or even negatively affected by the sacred aura of Valinor, unless an evil will works in disguise and with deceiving purposes to make it happen; and this is what Melkor/Morgoth exactly did in Valinor, poisoning the mind of Fëanor and other Noldor, spreading lies according to which the Valar had invited the Eldar to Aman to contain them in a 'golden cage', and prevent them to achieve power in Middle Earth.
The Elves don't need to gaze again at the World, because they are completely satisfied and at home in an enchanted and holy realm, and the Noldor finally understood this after all their sorrows and sufferings in Beleriand and Middle Earth.
It's true, Eldamar and Eressëa are quite separated lands/realms of Aman, and are not directly subjected to the influence of the Valar, but they are still embalmed by their holy aura, that grants them 'Immortality' (Valinor+Eldamar+Eressëa=the UNDYING Lands)
The 'last gaze' at the World is thus not necessary (especially for the Vanyar, because they love the Ainur and hate Middle Earth
) and impossible, since the Undying Lands were completely divided from Arda and placed in another dimension, exactly for 'cutting' any remaining contacts with the World/Arda; and, from the Silmarillion, we also know that the Eldar of Eldamar also travel a lot to Valinor and its extreme borders, and that, after the Kinslaying of Alqualondë and the War of the Jewels, Valinor is certainly the most populated area (and arguably always have been) since it occupies the main region of Aman, the enormous and evergreen Plain of Valinor
Valinor is, whether they like it or not, the 'ultimate goal' of all the Elves, a natural desire and longing of theirs for the Sea and the Immortal Shores, something they always look at and try to resemble even if they linger in the World; Imladris and Lothlórien were in fact 'mortal reflections' of the Splendour of Aman, and even Sauron, to convince the Elves to aid him in the forging of the Rings of Power, falsely promised that they would have been able to recreate the Bliss of Eressëa or Valinor itself.The Wounds of the World come from all the evil deeds of Melkor and his numerous servants, direct effects of the Ineluctable Faith of the World.