It might be just me, but I'm still far from certain that any romantic relationship existed between Uhura and Spock prior to the scenes in
Star Trek (2009) involving Spock losing his Vulcan cool on the bridge as a result of, in quick succession: A) destruction of Vulcan and death of his mother and B) Kirk's provocation pushing him the rest of the way over the edge, and the subsequent turbolift consolation by Uhura which suddenly turned into something more.
The earlier shuttleport scene (Uhura confronts Spock about her assignment to a ship other than
Enterprise) establishes at minimum a working relationship in which Spock was already thoroughly familiar with Uhura's academic achievements and professional qualifications, but goes no further.
[Not shown on screen, but part of the pre-release online promotional material from the official website were "dossiers" for the main characters, including:
View attachment 17629 View attachment 17630
Again, never shown on-screen, so not strictly speaking part of the characters' backstory, but it does--in combination with what we are shown--imply a previous professional association between the two (possibly growing out of a prior mentor / pupil academic alignment.) ]
At any rate, we're shown that they were clearly well-acquainted--perhaps even friends to the extent that Spock's characteristic reserve would make such an arrangement possible--but we really see nothing which suggests that a romantic relationship of any kind existed (or could exist) prior to the turbolift scene.
Whether or not the possibility of anything beyond friendship had ever consciously occurred to Uhura before might be debated, but what we see could also be simply her attempt to comfort someone she considers a friend, who has within a short span of time been dealt a series of heavy blows which have driven him to the point of emotional compromise. Uhura might not fully comprehend what it meant, but she would know enough to understand that the combination of events represented a serious shock to a Vulcan, and as a friend she would offer such support as she was able to muster on the spot.
This, too, would not be at odds with what we were shown in TOS.