A great many immigrants to the USA from Asian or African countries where the names are very different from those Americans are used to use pseudonyms when they become workers in retail and have to use name tags. It is quite possible that "Theary" is a nickname based on her real name that is the closest she or her employer thinks Americans can get to in easy pronunciation.
I had a student from Togo a couple of years ago who got a job in a grocery store working behind the deli counter. His name was Esenam (which I personally think people should have been able to deal with easily), but when he worked in the store, his name tag said "
Eric".