Answer:
Osteosarcoma
Explanation:
According to my research on studies conducted by various medical professionals, I can say that based on the information provided within the question the most likely cause of her symptoms would be Osteosarcoma. Which is a type of bone cancer that starts off in the cells that make up our bones. This is one of the most common cancers, especially in children, and symptoms include localized bone pain and swelling.
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