Tax Identification Number in US for International Tax purpose.?

A student, after her MS, working in US with F! visa. Now her US tax status is Non Res. She has filed her 2018 returns together with her husband who is having H1 Visa and US resident for tax purpose. She has shown her Indian Income in the tax returns and paid the tax also.

Now she has to file her tax returns in India for her Indian income. Now we have to write her US Tax Identification Number in the Indian Tax Form. She is having her 9 digit SSA number (In Form W-2). Let me know the 9 digit SSA number is the TIN number or different.