JJ younger sister

In which Jennifer Jareau 20 year old younger sister Amelia Jareau aka AJ works in the BAU but in a different building with a different team instead of with her old age sister JJ but what happens when Agent Hotchner And Agent Gideon asked for her? What happens when she had a one night stand before getting call in for a case and what happens when she surprise during this case she working with 27 year old IMF agent that she sleep with?