Because in spite of everything he's a good friend, and I think I'd know if he had feelings for me. Even if by some bizarre chance he does, nothing is ever going to happen between us.

[She means that sincerely. Maybe she doesn't know everything there is to know about Spock, but she knows him well enough to know that they have no romantic chemistry. They're friends, and that's all.

Smiling sympathetically and a little sadly, she says] Maybe it's time to do something about the way you feel. Then you'll know, one way or the other.