Sadness
The Niqols generally had simple relationships. Mutual attraction led to dating, which would transform into proper love if feelings were to bloom.
Those relationships were deep, intense, and strong, but they were based on how open the Niqols were toward their feelings. The aliens rarely went against their emotions, which made the interactions between partners straightforward. It was easy to understand whether their bonds only had physical attraction or had something more.
Even Khan, George, and Helen had found good partners relatively easily. The Niqols' straightforward approach to emotions and their lack of self-restraint had helped those humans get over the differences between their species. Things had been slightly different for Khan, but he knew that everything would have been harder with Liiza if she didn't reveal her attraction right away.