Mithadan, perhaps you overlooked the fragments of "Turin in Nargothrond" which were published in UT as part of the appendices to the Narn, where the Turin/Gwindor/Finduilas triangle is covered at some length (pp. 155-159). There we find
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...but against her will her love for Turin grew day by day....yet she knew he had no love of the kind she wished. His heart and mind were elsewhere
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and so on; all repeated essentially verbatim in CoH. This is a slight modification of the story in the Grey Annals from a few years before, where Turin indeed loved Finduilas, but refused to 'taint' her (or betray Gwindor).
More to the specific point of Gwindor's foresight and the Doom: in UT p. 159 CT says "of the Battle of Tumhalad and the sack of Nargothrond there is no other account," sc. than that used in the Silmarillion, which in fact is that of the Grey Annals (XI. 85), where Gwindor's prophecy appears, and so that text, the published Silmarillion, and the CoH are close to identical.
(with one puzzling exception: the paragraph which appears at the bottom of CoH p. 176, repeating the Silmarillion, does not have any antecedent I can identify ["Then the warriors of Nargothrond went forth, and tall and terrible on that day looked Turin...."])