Respectfully snipped to address:
According to what has been written in the media, Whitney Huston's estate has nothing to do with Bobbi Kristina once she would die. It sounds like provisions were made within the trust that Whitney set up that if Bobbi Kristina is deceased, the beneficiaries of the trust are her sister and her sister's children.
If Bobbi Christina was close in age to the time she was due to receive another huge payout from the Whitney Huston trust, it could possibly be of benefit to a potential benefactor of her (Bobbi Kristina) will to try to keep her alive, even if on life support, until that payout is made.
Questions: 1.) Does Bobbi Christina have a will?
2.) Who are the potential benefactors in that will?
3.) When is the next lump sum payout due from the Whitey Huston trust?
If a person dies intestate (without a will) the benefactors of the estate are determined by the state laws for intestancy in the state of residency of the person who died. Usually parents and siblings come first, then it gets into grandparents, aunts, uncles, and cousins. There are often established percentages already established within the laws.
If Bobbi Kristina is a resident of Georgia, it would follow the Georgia State laws, which would be online.