I've seen her typed as ESTP & ESFJ. I think she's way too romantic to be ESTP. I'm watching Behind The Music and people close to her are saying she believes in the 'fairytale' and all that. I'm thinking aren't ESTPs a little more realistic than that?
I remember an interview with Ben Affleck and he mentioned she kind of prude. She says she's very traditional.
YouTube - Jennifer Lopez Good Morning America Interview (Wed 22. April 2009) Fights Whooping Cough
YouTube - Jennifer Lopez Talking About El Cantante