Sister spent all dad's money. What now?

My father was murdered in Hawaii. He moved from new Jersey to live with my sister. He had dementia, sold house before moving and was due to use money from house sale for a nursing home, which my sister never did. We found out that both my dad's life policies had been cashed. She changed the beneficiary’s name, which was both her and I, and cashed policy early. The money from sale of house in not in his bank account. The executor lives in New Jersey and has not received the original Death certificate as sister keeps stalling. He has already been cremated (not his wish). We applied yesterday by post for a death certificate. We also contacted the bank as my cousin was still named on his account and the balance is €17.000.00 so, his money is missing. Do I need a lawyer? What are my options? We downloaded the bank statements and money has been spent all over the place. She wrote herself a cheque for 200.000 as soon as the house was sold, although she did have to sign off on it. The house was due to be split if sold, but this was done before death. I also know if you are named on a bank account you can spend on it.

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