[Galin]

According to the Grey Annals it could have been as much as 52 years before Galadriel passed the Ered Wethrin from the north (it's the first mention of her visiting Thingol in any case), but my guess is that it was around 18-20 years rather, and that Galadriel perhaps passed over for the Mereth Aderthad. Granted it could have been sooner too, but there is mention of Angrod meeting with Thingol and the text is silent about Galadriel.

So if she first crossed for the council, it's arguably memorable...

... a host crossing this mountain range to this historic great council and high feast (historic enough to be named and remembered). Plus, if I recall correctly, this could have been Galadriel's first major mountain range crossing, no matter how long she lived on the north side.

When T wrote that passage it's pretty clear that his idea, at the time, was that Celeborn was a native Silvan Elf and Galadriel had met him in his own land of Lorien, where he had dwelt since the arrival of the Danians/Nandor before the Sun rose.

I agree Tolkien had a different history in mind, but how clear is it really when we take away draft texts and Christopher Tolkien's commentary, considering only the texts that Tolkien knew his readers would find on bookshelves. Even if the reading in The Lord of the Rings itself suggests Galadriel leaving Beleriand before the fall of Nargothrond, the history also reveals that at the end of the First Age, after the fall of Morgoth, Galadriel crossed the Ered Luin (now specifically named) with the Sindarin Celeborn (published by Tolkien in RGEO)

By "mountains" Galadriel could have either meant the Ered Luin or the Hithaeglir; either way doesn't really affect the meaning.* The one really significant bit is the suggestion, never subsequently contradicted, that Galadriel had left Beleriand before the end of the Elder Days.

If she could have meant one of two mountain ranges, why not another?

I don't know if I would call the RGEO information a contradiction necessarily, but it should factor in to any interpretation in my opinion -- not that you aren't or didn't, I'm just generally noting it.

If one wants to bring in the late writings then the reading fails that way as well, since Galadriel was with Teleporno the whole time since before the Exile.

I never bring in this late writing since it fails itself, on major points, to agree with already published (by author) text. And to my mind we can't know if Tolkien himself ever meant the reader to think any of this late account was true.

I doubt he intended readers to know that Celeborn was once a Silvan Elf... granted, the adumbrated text being so late, and its mere existence, arguably suggests "intent" in some measure, but even Christopher Tolkien's comments about this text appear to me to be a best guess, and I think Tolkien's memory is still a possible factor here (concerning what was written versus what was published).

*I now really don't recall- I imagine HME covers it- when it was Tolkien decided that Beleriand had been located west of the Shire, that Lindon was its last remnant and the Ered Luin its old eastern fences; was this before or after he wrote the Lorien chapters?

I don't recall at the moment either, but it's interesting that the mountains of Galadriel's speech were seemingly once -- albeit in a draft passage differently expressed -- the mountains of Valinor. Which means nothing really except that if true, after the mountains "arrived" they changed in conception... so maybe once again?

In any case I realize some may think the above reading strained, as you do. So far some do, some don't.

But that's why I test it out