Owner sold an already sold land to mother. What should we do?

This case is related to a piece of land bought by my mother. The owner had already sold it to someone else before selling it to us.She is alone lady(widow) and this is the only property she has.She has spent so much money in hiring lawyers but nothing has been done.She is finally thinking to give up.Is there any way by any chance the case can be in favour of us ?Any legal advice? Thanks in advance, Her daughter