Louanne age 9 was the first micro Annie in June of 1979 replacing Patricia Ann Patts in second national tour.
Perhaps the producers were rather harsh in how they handled the situation, but Joanna is certainly not the first child actor to be let go in a role. I saw Brittny in the role during the pre-Broadway run in Hershey, PA (Martin, Charles, and Thomas were all there; I met them at intermission). It was a couple weeks prior to the Broadway transfer and right around the time of the announcement of the firing. My friend saw one of the last performances of Joanna in the role, also in Hershey. Oddly, I thought Joanna was a better singer and actress, at least from different clips that I saw. Oh well, that is show biz for you. Many different factors play in a decision of that nature.