We're aware that she is a good Care of Magical Creatures teacher, which means that she probably had a lot of experience in the subject. However, the previous COMC teacher was Prof. Kettleburn, as mentioned in the book:
"As to our second new appointment: well, I am sorry to tell you that Professor Kettleburn, our Care of Magical Creatures teacher, retired at the end of last year in order to enjoy more time with his remaining limbs. " —Albus Dumbledore at the 1993 Welcoming Feast
So she didn't have any teaching experience as such and nor was she a retired Hogwarts teacher. Clearly she didn't have much to do as she obliged to teach the Hogwarts students whenever Dumbledore asked her to. Which begs the question-what was her actual profession? Was she like Newt Scamander, but after the glory days?