Who is Valerie Jarrett?

I first heard of her from the NEA conference call:
"We have about 20 folks and we work under Valerie Jarrett, she's one of our fantastic leaders."

Now I found this:
http://frontpagemag.com/readArticle.aspx?ARTID=36289
"Jones owed his elevation to another new factor: the unparalleled influence of Valerie Jarrett."

"The president makes no decision without her and has said she can 'speak for me.'"

“If you want him to do something, there are two people he’s not going to say no to: Valerie Jarrett and Michelle Obama.”

“I trust her completely…She is family.” Obama trusts Jarrett “to speak for me, particularly when we’re dealing with delicate issues.” When asked, he admitted he runs every decision by her.