My grandma won't help me financially and I am stuck. I gave up everything for her. What do I do?

She can't get services and she is well off. Let's just say she has money and I am suffering. I lived with my 100 yr. old grandma for 7 yrs and now she can't be left alone. I am also struggling to take care of my son. What do I do? I can't pay my bills and going in debt. I am the only one out of 6 grandchildren who takes care of her, no one visits or talks to her. 7 yrs ago, my mom asked me to take care of her, I dropped out of college, rerouted my son's school, and moved 500 miles away from my immediate family. I kept my promise to my mom even though she passed from cancer 3 yrs ago. A month ago, I lost my dad and I couldn't be with him, because I was taking care of my grandma. I am getting depressed because of this. My grandma's 89 yr old brother is her POA and pays her bills. I approached him about it and he tells me she doesn't have the finances, but I believe that to be untrue. I know what my grandma has and in no way am I using her for financial gains. In no way the amount I desperately need per months breaks her piggy bank. What do I do? I can't even work because I can't leave her alone. Just recently I helped her recover $ 6,300 in assets and thought she would be able to help me and she says no!!! That was my mom's money. I can't take it anymore!!!