Chemistry
Disclaimer: I don't own Zoeyy 101, Nick does.
She was often blind about these things. You know the kind of things that people have when liking someone. Look at Chase and Zoey, for example, they both had chemistry, even if they were too shy to admit it.
The ironic thing was the fact that Quinn had a boyfriend as well. But sadly enough, she didn't see that Mark wasn't the truly the guy for her. Even though Quinn always followed facts, the only thing that made sensed to her.
But love, never comes easily for anyone. The fact is that love rarely follows facts, only emotions that stomp out all logic.
The fact is Quinn was in denial. She didn't have the same kind of chemistry that Zoey and Chase. She didn't have any chemistry with Logan.
So why did her heart beat a little faster, and gets butterflies in her stomach when ever she sees Logan?
Quinn might be in denial, but others can perfectly see that she had chemistry with Logan. If only she could follow through with those facts, and if only Logan can follow through as well.
But like in chemistry, where mixing the wrong chemicals results in a catastrophic event, Quinn knew she couldn't touch Logan. Not even a little bit.
Besides, she had a boyfriend. And that was more than enough chemistry that she could follow through.