Co Tenant break the agreement refuse to pay advance amount back

My mother in law 63 yrs and her neighbor 40 yrs (lady) has signed a rental agreement with the intention to start business. But the neighbor has decided to discontinue, 4 days before the the start of the business. Advances were paid to the landlord from my mother in laws bank account.The referred business had no partnership agreement. So in this situation, even before the start of business, there are lots of payments due, and primarily the rent to the landlord. She refused to pay any amount for my loss. What is the way forward to recover the loss?