The proceeds reported on the 1099-S should go on the return for your mother's estate (Form 1041). To prepare an estate return you need TurboTax Business. You can visit the following link to purchase the program: TurboTax Business.
TurboTax will take you through an interview to prepare the estate return, similar to the personal (1040) products. As part of preparing the 1041 return, TurboTax will prepare K-1 forms for each beneficiary. They will need to enter the information from the K-1 into their personal 1040 returns.
