Miles hears Jacob's last thoughts, reveals Ben killed him

As Ilana, Miles, Frank, Sun and Ben are making their way to the beach camp, Ilana questions Ben's honesty about whether the smoke monster really killed Jacob. She knows about Miles' ability and asks him tell her what happened to Jacob using the pouch of ashes she took from the four-toed statue.

Miles rats Ben out, revealing that Ben actually killed Jacob and was standing over him holding a bloody dagger. Ben tries to deny he did it and Ilana reveals to them that Jacob was the closest thing she ever had to a father. The group then continues towards the beach.

So what exactly is Ilana's relationship with Jacob? How did they meet and how long ago was that?