The first time Beverly noticed it was when she saw Alyssa beaming a ten-terawatt smile in the direction of Dr. Selar, and she made a mental note to talk to the young nurse about the rarity of Vulcans becoming involved with other species.
A month later, she noticed Selar pausing in her work during a slow day to observe the nurse, and wondered if maybe she shouldn't have had that talk, after all.
The number of exchanged looks and smiles (at least on Alyssa's side) increased after that, until one day, about six months after Beverly first noticed something was going on, she saw Selar enter Sickbay a couple minutes early for her shift, step up to Alyssa, and say a quiet word, while unobtrusively holding out two fingers, which Alyssa lightly touched with two of her own.
Shaking her head in amused disbelief, Beverly stepped into her office, giving the two some privacy. That certainly explained why her head nurse was glowing lately, and why the Vulcan doctor seemed… as happy as she'd ever seen a Vulcan.
"Good for them," she murmured to herself, pleased.