@sammywinchester, Hi Brianna. Welcome to Mayo Clinic Connect. The world needs more young women like you who are interested in the medical field. I hope you continue to be fascinated by diseases and blood disorders because they are quite amazing. I had a very aggressive form of leukemia and a bone marrow transplant a few years. Wow, talk about immersion into the world of blood cells and their nuances. I got quite an education and hold a deep appreciation for what our bodies are capable of overcoming.

From my understanding, sickle cell anemia is an inherited trait and it is not reversible. So the likelihood of all of your sister’s cells becoming normal wouldn’t be expected. If a child has one parent with the trait and the other doesn’t have the sickle cell gene, the child will have both sickle cells and normal red blood cells. Sickle cells die off faster than normal red blood cells. Right now her body may be producing more healthy cells, which is great. But from everything I’m reading that wouldn’t reflect a total reversal of the diagnosis of sickle cell anemia.

Mayo Clinic has a good informational article that explains in better detail than what I highlighted. It would be amazing if her condition turned around on it’s own. But the only way for that to happen would be through a total remake of her immune system with a bone marrow/stem cell transplant.
https://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/symptoms-causes/syc-20355876
That actually might be a good question also for one of the nurses or doctors overseeing your medical assistant training. Is your little sister on any treatment for her sickle cell currently?