What should be done about an aunt who's daughter is neglecting her Mom for sometime now?

I am one of her nieces, from Detroit. My oldest sister daughter moved to cailf, two years ago. She has been trying to visit, her great aunt, when she can. Now it as become apparent that it very very bad. My sister just got back, from one week an from what she described. Was they both have lost so much weight. My cousin is very cruel to her mom, she curses at her. Apartment dirty the phone has be cut off, so when she goes out. My aunt with dementia is just left there, without communication. At one time my cousin was on drugs, I believe thats when she moved in with her, about five years ago. that's when my aunt started to go down. I leave on Feb 4 thru the 11 for a visit. I would like very much, if. there is someone I could talk with. My aunt doesn't need to live like that, my mom past in 09. So my aunt is the last one in her generation. I hope to have someone there whom, I can get some help from