My best friend changed his whole life around to take care of his dying grandmother. His family has turned against him since then in order to use her money to pay all their bills. My mother and friends say that power of attorney has full control over everything but others say that the healthcare advocate has the power over anything to do with her health. He is in a constant struggle to just pay for someone to take care of her while he works. And is receiving no help from his family.
And who has Power of Attorney for her?
How it should work, is that decisions about where and how grandmother is to be cared for are made by the healthcare advocate. The expenses are then paid using grandmother's funds by the POA.
If the POA disputes the healthcare advocate's decision - for example, perhaps because the grandmother does not have sufficient funds to pay for the services the healthcare advocate recommends, or because the wider family has concerns about the quality of care being provided - then the two need to discuss what options are possible.
Do you have a reasonably clear idea of what the source of conflict is? You say your friend's family has turned against him so that they can use grandmother's money to pay all their (own) bills; but objectively speaking, it's very improbable that they would see it like that; and it's important to remember that grandmother gave the person she chose the authority to act for her - it happens, but again it's unlikely she would have picked someone who was going to keep all the money and refuse her the care she needs.
What's much more common is a disagreement about where grandmother should be cared for. If, for example, the POA does not agree that grandmother is best looked after in your friend's home, it will go against the grain to support what the POA sees as a bad decision by co-operating with it (s/he should, but there's no point in being surprised that s/he's obstructive). So: what are the issues, and how might they be resolved? The answer should certainly not be for your friend to be paying for support out of his own pocket.