[Joann37]

She's a little girl! You ask how a widow and two children are to survive? First of all, I'm sure they have millions, so $ will not be a problem. But even if not the case, why would you expect an eight-year-old to contribute to her family's finances?

You also state that she needs a life and purpose. Sure, but at eight years old, shouldn't she just concentrate on attending school and getting through the loss of her father with the rest of the family?

[khnyny]

The circumstances of this family are quite unique.

[Essie]

From what I've read when her father was killed, he was filming a segment for Bindi's upcoming show. They didn't decide to get her actively involved after her father died. Plans were already in the works. Doing as much as possible will probably help her and the family get through what must be a very difficult time.

[Jedi Master Pikachu]

As MarkL points out in comment 12, it is something for the family (immediate family) to decide. They would know how Bindi would react to being in the limelight, being famous, etc.