This is terrible for your friend, but it makes me wonder what is taking so long.
I live in California and went to H&R Block, like I'd always done. My tax guy actually came to my office the next day and told me that he couldn't complete the filing because someone had already filed using my son as a dependent. It was, of course, my ex-husband. I was furious. I contacted the IRS right away and they told me the forms I needed to complete. They asked me to get a letter from my son's school stating that he had always attended school there as my husband didn't even live in the same city. I also provided papers provided to me by the county child support enforcement division that clearly named my ex-huisband as the non-custodial parent.
The woman I talked to at the IRS was very nice to me and she said that if everything I had told her was true, I would get my refund, but it could take up to a year to get it straightened out.
I sent everything by certifified mail for both Federal and State taxes. I was shocked when 4 weeks later, my refund was automatically deposited into my bank account. I had obviously proved that I was the one who had the legal right to claim my son. They sent me my money and then went after my ex-husband. He had to pay them back, plus fines and interest, AND, he was not able to even file for earned income credit for 10 years whether my son ever went to live with him or not.
So, I know things can be more complicated if a person has passed away, but she is the one who had the legal right to the refund. That's not hard to prove. It could be that they are going over all her forms in greater detail. I had just a simple return, no itemizing...nothing complicated. Your friend isn't the one who committed fraud so most of the investigating should be done with regards to the other person who did.
Tell your friend to hang in there. I believe that things will get straightened out. Tell her to keep trying with the IRS until she finds someone more helpful. I was so lucky to get someone awesome right away.
Best wishes.