I think it’s very nice of you. If she’s in the phone book, looking her up is welcomed. I’d also include my phone number and email on the card, should she prefer to get back to you that way. There’s no down side to simply sending a former teacher a kind note. Being 80, I’ll bet she will really be touched.

Once, my son had to write a letter to an author for school. He wrote to an obscure author whose books he read passed down from my husband, so they were no longer in print. My son got a personal, hand written letter from the elderly author who expressed his enormous joy at receiving the letter from a child.