Inside the shuttlecraft, Uhura was having a hard time getting through to Spock. She didn't care that Kirk was also a part of their conversation. It was almost a good thing. She wanted answers from Spock and she wanted them now. Having Kirk with her might let Spock surrender quicker. She enlisted Kirk's help to get some sense into him when she said, "The Captain thinks so too."
Kirk was quick and asked to not be involved, when after a second, he agreed.
Spock finally answered in his very Vulcan way of how much he loved her to throw away his life for her. Uhura had a warm feeling in her stomach and tears in her eyes, when out of the blue, they were attacked.
A/N: This is short, but I think that moment in the movie encapsulates Uhura's implicit trust in Kirk.