How can I ensure my grandma is being cared for properly?

Please excuse the length of this post, but I find it necessary to explain my question. In 2012 I had a very clear conversation with my grandma regarding her wishes for POA. I didn't want to have this conversation, but she wanted me to hear it. She expressed that she wanted her niece to be POA, because she didn't trust her children. That made perfect sense to me at the time. Her children never called, visited, cared. Her niece and her had always been close. Like a daughter she always wanted. After my grandpa died her niece would take her out ahopping, to lunch, to church, even before he died she had very much been like family. Anyway in 2015 roughly 3 years later my grandma took a bit of dip, she was injured and her mind wasn't fully there. At this point I heard my uncle was now POA, which i found odd as he never really cared about her, but I let it go. In May( of 2017) my lease was up, and I move into my new apartment in July. So in between I am staying with my grandma and the niece (she had moved in a while back and just cares for her, cooks, cleans etc).

This weekend the hot water was shut off, for the last few days there has been no hot water due to an outstanding bill from April. And I found out this happens all the time. And my grandma has several bills in collections. My uncle never pays them. I spoke to the niece finally about the POA situation. She explained that in 2012 my grandma brought her to an attorneys office and gave her POA. That she had wanted someone neutral not in the will to handle her affairs. But when my uncle found out in 2015 he made her change it. And took her checkbook. This whole situations just seems wrong. I want to do some fact finding, obtain copies of the bills that have gone unpaid, but I don't really know how to navigate this mess. Apparently this happened in winter also and instead of no hot water there was also no heat for days. Also he changed oil companies to avoid paying the past due bill from April.