Suspect abuse by my mother's financial POA. What can I do?

I'm the former agency, only child and heir. I need legal advice, prefer from an attorney in Probate, Elder Law and Adult Guardianship cases

My Mother Rita is in pretty good physical health for her age at 87. However, her memory loss and dementia is increasing every year since 2010, when my small family and I first noticed it. I am her only child. My husband passed in 2004 and we had no children. My Mother’s parents passed in 1980’s and then my Mother’s only sister passed in 2013 and that’s when all the problems started.

My Mother married my Father in 1950’s. He passed leaving my Mother with some money. Then my Mother married another man, Homer, who was very wealthy. He passed of a heart attack and left my Mother his Estate worth 7.5 million. Million dollar mansion, airplane in the attached hanger, new Mercedes and Ford Pick-up Truck in the driveway, and lots of money, etc., etc., Homer also left my Mother a 29,000 acre ranch with working Deer Lease, goats, etc. Homer left her with a thriving engineering consulting business with an office building. Homer, was good to me. He raised me. He helped me through college. He had no children and wanted to adopt me, but never got around to it. I miss him

After his death, my Mother married her 3rd husband Lynn. My Mother was approximately 67 years old at the time, very charming, educated and worth millions. She met him at a “church dance” and they married 1 month later. What man out there is going to marry an average 67 year old woman, beautiful, sexy or not…..without $$$$$$. Let’s face it, I know a lot of men and NONE of them would. Men are as much of a “gold digger” or wanting a “sugar mama” as women can be.

My Mother is now 87. Lynn is now 92. He would never divorce a “cash cow”. He is living “the good life” at the super upscale nursing home they are now in. The first 10 years of their marriage they spent that money!! They went to Europe about 5 times per year, for 10 years straight. That’s fine, I would have too. What they did before is okay. It’s what’s occurring now that I’m very disappointed, upset and concerned for my Mother’s well-being.

Lynn at 92 is declining physically, but he is mentally sharp, alert, memory good, but he is cunning, calculating, planning his next moves and I know up to no good with my Mother's finances. $7.5 million dollars can go a long way since they have been married. It should last most people a lifetime, not just 20 years or less. They’ve spent a lot of that money in the first 10 years. However, now that my Mother has increasing dementia, I believe he has misappropriated funds for the last 7 years of their marriage to HIS benefit and the benefit of his only daughter and her family. The man hates me, because I’m sure he feels I’m in the way to his “ultimate” goal which is to take everything financial away from my Mother’s Estate and leave me with $0.00. I’m sure he had this planned all along, to give everything that my Mother has worked for, that Homer has worked for, that my Father had worked for and give all that is left after her death, to his daughter Lisa and her family. When my husband passed, I was left nothing but debt that I had to pay. I have no children. I have no grandparents. I have no siblings. I absolutely have no one to care for me in my old age. I live simply now and have for the past 20 years, to save what I earn from a job. I’m now 60 years old and thinking that I will NEVER be able to retire or stop working, because I don’t have the money to do so. I’m not greedy, but I do think about this a lot. I think how my Father, Homer and my grandparents that my Mother inherited from, would NEVER want this to happen to me. They are rolling in their graves about this. For me to live like a pauper in my older years (possibly homeless) while her 3rd husband and his family live high on the hog in fancy houses and Lynn in an upscale nursing home not sacrificing a bit.

I have not obtained my Mother’s medical records yet, but I plan to. My cousin in Dallas is a family physician and he too is planning a trip to Houston and wants to review the records going back to 2010 or more to figure out when her dementia or Alzheimer started. My cousin and I both suspect fraud and misappropriating of funds, that Lynn is taking advantage of my Mother now of her declining mental capacity and putting money of hers in trust funds, investments, etc. for the benefit of himself and his daughter, son-in-law and 2 grandchildren.

Since my husband passed in 2004 and Rita’s only sister passed (her closest confident other than me), her 3rd husband Lynn is keeping me from knowing my Mother’s health, knowing anything about her financials, he’s keeping me from seeing her on all major holidays, including Christmas, her birthday, etc. Once my Mother’s sister passed in March 2013, 2 months later he takes my Mother to an attorney and forced her to sign new POA's taking me out and his Daughter & Son-in-Law in. Respond.