Lorelai and Chris dance together beautifully, symbolically showing that they have sexual compatibility. See how happy they look together, enjoying each other’s physicality and natural playfulness, while Miss Patty presides over them approvingly.
In contrast, Rory and Dean dance awkwardly together, looking nervous and unsure of themselves. It suggests that they are not sexually fluent, being inexperienced teenagers, and is perhaps a sign that there is something lacking in Rory and Dean’s relationship. Tellingly, Miss Patty worried that Rory might hurt Dean with her bad dancing – a foreshadowing of the pain she will cause him.
The Annotated Gilmore Girls 