mortgage of property of a relative

Usually, the Banking Institutions do not sanction loans on the security of the third parties who are residing in some other Countries.  If your sister-in-law is account holder in such Bank, there may be little chance.You did not state whether you are going to obtain loan from a Bank or an Individual. First of all,  please contact  your Banker to ensure about its willingness to forward your loan application. However,  I am of the opinion that In such cases, your sister-in-law has to give a special Power of Attorney to a trusted one, empowering him to execute necessary loan applications and other  forms of Banks. The said Special Power of Attorney  is to be executed in presence of Attorney-Notary which needs to be revalidated in India.

Education Loan is availed only by the student. He can apply and the sister in law can become guarantor. Her property can be given as collateral.

There should not be any problem. The bank can prepare the papers and the same can be sent across to be signed before the proper authorities about which the bank would guide you.