This simple scene is, I would argue, the foundation of Steve and Kayla and the true beginning of their relationship:
Here, thinking he might not see her again, Steve opens up enough to ask Kayla if she still thinks he killed Britta.
When Kayla asks if he loved her, loved Britta, I think she is inviting him to open up. I love that Steve dodges the question, because I think that fits where he is right now. (I do think he still loves Britta at this point.) But what he does say is important too. The most significant thing about Britta is that she loved him. He’s saying that he could never kill the only person in the world who loved him. And, perhaps more importantly, he admits that it is important to him that Kayla believes it.
Kayla doesn’t answer right away. Such a small thing: “I believe you.” I think that Steve doesn’t quite realize that for Kayla, this is a commitment. It’s not just “I believe you, good luck, have a nice life.” If she believes him, she has to act on that belief, she has to help him fight to prove his innocence.
No wonder she is hesitant to say it.
After this, I don’t think Kayla ever stops acting on the belief she pledges here. She stops pushing sometimes, but it’s never by her choice — and even then she usually comes back fighting. Steve is about to find out what it really means to have Kayla believe in him, and it is going to be a lot more than he bargained for.