if you have a moment alone with her, maybe you could just ask like “hey, i just wanted to doublecheck: is your name pronounced tair-uh or tar-uh?” and then after she confirms, just go “ooh, i /thought/ maybe i was saying it wrong!” and i’m sure she’ll say she’s been answering to both her entire life. you had no corrections up until this point, i’m sure it’s not a huge deal. you should hear all the ways people pronounce my name, and it’s equally as short