Harriet Critchlow Syndrome 

When a nerdy girl undergoes puberty and develops a pleasurable aesthetic and personality change, appearing as if undertaking more sexual acts ( a girl gets hot and slutty out of nowhere)

Guy:" Dude, did jenny fletcher get hot all of a sudden?"
Dude: "oh yeah man, shes got major harriet critchlow syndrome."

Harriet Critchlow Syndrome by master-pwanker September 18, 2015