In Batman Begins, Bruce Wayne is abroad to study the criminal mind and to join the League of Shadows for several years. When he returns to Gotham City, Rachel - his "oldest and best friend" - hears of his return from the DA and later meets Bruce by coincidence. Bruce is a little speechless since he just played his billionaire playboy act (buying the restaurant so that his girls could swim in the decorative pools) but would like to show Rachel that he is more than that.
So why did he wait until Rachel bumped into him instead of contacting her when he returned to Gotham? Surely calling his childhood friend would not be out of character or raise any suspicion.