I think fruit puree is better than fruit juice because it contains fibre as well. Also, it helps bb to practice how to swallow and chew so that when you give her more solids later on, she will eat it more easily.
At 6 months, bb should start eating fruit puree and vegetable puree as it contains lots of important vitamins that a bb needs. YOu can mix different tastes so that bb gets a large variety - it will help make sure that they do not become fussy eaters when they get older.