LANE: I’ve never really felt this way before. I mean, Henry – yes, but we never spent any real time together. It’s not just puppy love, you know, it’s different.
Puppy love is an informal term for feelings of romantic love experienced by a child or someone in early adolescence. Often these crushes are on someone that the young person doesn’t know, such as an actor or pop star. Lane seems to be saying that her attraction to Henry was not only immature, but barely based on reality, as she didn’t really know him.
The Annotated Gilmore Girls 