It happened rather quickly, Spock and Leonard entering into their relationship. Leonard really hadn't been lying when he said he'd liked the fella.
It happened like this: after a month on the Enterprise, Nyota and Spock had known that any more romanticism between them wasn't meant to be. Spock had known this because he was not getting a sense of tension from Nyota. Without this tension he could not help but see a lack of forward progress available between them. Nyota had this known because she couldn't help but see Spock's restlessness as the dissatisfaction it was. In short, neither of them was what the other was looking for in a romantic sense.
Spock, however, made a great acquaintance for Nyota—who else would be willing to review a twenty page article about antenna gestures between andorian sibling of the ages seven to fifteen for her the day before it was due for publication, and at one in the morning with little more than a "your writing style is engaging and is more than a suitable replacement for meditation, I would be pleased to be of aid."
Nyota, in turn, did her best to be a great friend back—the stableness of their relationship apparently meant that Spock thought she was "a much needed support structure and would always hold a unique standing" in his life. He'd, thankfully, had the foresight to tell her this over a private meal in his quarters, handmade with as many traditional vulcan ingredients as were available given the new circumstances of Vulcan. They slipped from being one type of family—the couple without children—to another type of family as simply as that.
What Nyota had done for Spock was notice what he'd said he needed from her—somebody who not only supported him, both spiritually and physically, but who also challenged him to the point of maintaining a dialectical thesis, antitheses, and synthesis relationship—and notice who was giving him these things. And she'd made her move then.
Nyota walked past Chapel, a small look assuring her fast friend that she was alright, towards the back of the infirmary, paused, and took a deep breath "Doctor McCoy, I need to talk to you."
McCoy jumped, bumping his head against the cupboards above him, and glanced with a beet like face at the dated time display wrapped round his wrist. "Yeah, that's fine, I got off shift 'bout half-hour ago." He glanced up then, colour suddenly drained from his checks, "It's nothing serious, right?"
Nyota widened her smile, speaking with a measured slowness, "It's nothing harmful, no, but it's certainly important. And private" She nodded her head at his office door, the clear glass reflecting the mechanical tools behind her into view.
"Yeah, sure, follow me." McCoy walked the five steps to his office, where he had to key in his passcode twice, being that he wasn't supposed to still be working. Inside the room he set himself behind the maple desk, and pulled out an unlabelled bottle, after which he peeked at his guest before continuing on to lift out two glasses. Then he motioned her in. "Would you like one?"
Nyota, sitting down, couldn't stop the upturn of her lips. "No thanks, but you might want both." Before McCoy could do more than open his mouth in question, she continued with the killing blow, "Spock likes you."
"Huh?" A paused followed, then, the sound of syrup gold liquid splashing into a glass. A swallow.
Nyota leaned in, again before he could recover. "Spock likes you back." She stayed still, waiting until McCoy looked her in the eyes, before leaning back into the cushioning of her seat.
McCoy let out a chuckle, "Huh," he scratched slightly behind his ear, as though he could feel it was heating up and was trying to do something about it "I was about to ask if it was true." His blush rises, "Not that, I mean I didn't know—I was just going to ask if you two had really called it quits. Uh . . ." McCoy poured into the second glass and lifting it off his desk to hang in the air between the both of them, "Are you sure?"
Nyota nodded, arms relaxed and resting to either side of her. "I'm fine." McCoy, permission granted, swung his arm towards his mouth and swallowed. "And yes, we really called it quits, despite Spock needing someone just about now." She held eye contact before rising from her throne-like chair after some seconds, knowing the rest would work out.
And it had worked out—McCoy had waited until the next day to go see Spock, not sure the other didn't in fact know enough about human culture to not appreciate alcohol on someone's breath alongside a love confession.