Collider wrote...
This. In the second conversation she's talking about being together. Basically just because she's interested in you because you know about the protheans. Wow. And if Shepard starts the romance he says "There is something between us." Uh, Shepard, like what?
With Tali, you have the precedence of friendship. That's really important. Not only that, but the very important element of trust. She asked you not to reveal her father's work and Shepard agreed. They trust one another after all they've been through, they feel secure in one another's arms. I think it's very romantic, in that regard. Plus the butterflies and sunshine thing Kasumi talks about
The point of the romance was that she had feelings for Shepard she was afraid to act upon. In ME2, you console her and tell her that you feel there is a connection, then the next issue is the simple act of being together. Weak immune system, incompatable body chemistry and all. But they overcome all of that by simple trust.