Nyota knows she is not the same girl she was before she entered Starfleet. Whereas before she was always light years ahead of everyone else, here she is on par with several others- albeit extraordinary others, but others all the same. She has to prove herself here and she has to work harder than she's ever worked in her life. Most days it is worth it. Most days she comes home and she is satisfied that she could not possibly know more than she does now, or be in better shape or be any happier than she currently is.
Then the annual commander's ball comes along and fucks that all up. Every single, goddamn year.
It's not that she doesn't like attending it alone. iIt's not./i It's just that she hates all the drama associated with choosing someone to go with and the looks of pity placed upon those who don't go with anyone. Gaila certainly, could pull off going alone, but that's mostly because she can walk right in and choose whichever gap-mouthed member of Starfleet she wants and make them her date, regardless of whoever that person had shown up with. And Spock could secretly have his own harem akin to Noah's Ark with a girl and guy from every alien race, all stowed away somewhere in his quarters, and istill/i he'd show up alone and not raise any eyebrows. But Nyota is considered frigid by about 85% of Starfleet's males, so if she shows up alone, there will be snickers.
So every year when she enters the dining hall and it's magically covered in advertisements for the damn thing, she always feels a little pit in her stomach. It's worse this year when she comes home all grumpy and Gaila looks up sympathetically and offers to be her date. She loves Gaila, but she doesn't want to go and be the center of attention with her, and she doesn't want to have to explain herself to Spock, not just yet. But Gaila's pouting and looking so damn hopeful and suddenly going on about how she used to get smuggled magazines from Earth and she'd dream about going to a prom with someone she loved, ireally/i loved and who loved her back. And even though it's at the tip of Nyota's tongue to say no, she just can't say no to Gaila, not when she's smiling like that, not when she's admitting to something so obviously embarrassing to her, and certainly not when she's kissing her ithere/i.
Spock, she decides, is just going to have to deal. If he really holds her in as much regard as he claims to, then he'll realize Nyota isn't just being flimsy with her feelings. She genuinely loves both of them and can't imagine not having both of them in her life. She also can't help herself later when she dreams about what it would be like if they all got along and were a family.
The next night, though, she has the same dream while she's lying in Spock's arms. When she wakes up she knows he must have seen it too, because she's left alone.