1 - If your Mom's lawyer doesn't now how to challenge the trustee's decision then your Mom needs a different bankruptcy lawyer.

2 - Tell your Mom to get a professional appraisal on the house, not just guesswork. She'll pay $400 to $500 for it but it will give her lawyer something official to work with.

3 - The alternative is for your Mom to withdraw the bankruptcy and you and your sister come up with the money to pay her debts so she doesn't lose her house.