Here's Pub 559 https://www.irs.gov/publications/p55...link1000201749
, which says to ask the payer to separate the 1099 into one for your mother and one for her estate. If you can't do that, then report it as "Nominee Interest".
In TurboTax, you do this by entering the entire amount in Box 1, and then on the next screen checking the box that says "I need to adjust the taxable amount". Enter the adjustment (the amount you want to allocate to the 1041) as a positive number. Then select the radio button that says "I received all or part of this interest for someone else (I am nominee)". If it's a 1099-DIV, it works the same.
Pub 559 also says that you must give the nominee (the estate in this case) a 1099.