Is this possible

My grandmother had a lot sold at a tax sale in Sept. 2016. I personally went and redeemed the property on March 27 2017. In August she got a letter saying she owed another $800 for lawyer fees that weren't ever turned to the auditors office. She offered to sell the lot to the people that bought it for $6000 which is almost $3000 less than she wanted for it. She never heard anything from them about this. She received a letter from their attorney 3 days ago saying that she had to pay them $250 a month starting on December 15 2017 until July 2018 to avoid getting sued. I need information on what to do. The couple still has not turned the tax voucher from the sale back into the auditors office to get their money back. What do you think? Thanks