I'm pretty sure Tax ID # = ITIN (Individual Tax Id #)
You can work with ITIN; provided that they don't make you fill out an I-9 form. That being said, ITIN is not interchageable with a SS#, nor does it give the person the right to work. It's mostly useful with smaller businesses that can pay you on a 1099 tax form with no extensive background check and etc.
If she's going around filling out any job applications using the ITIN, it's only a matter of time before she gets screwed.
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Bio Date - 02/22/18 (walked in 2/15)
Expiration - September '18
Approved - 04/09/18
Naturalized via MAVNI | April 2018