Complex sentence: However, as the girl grew older, the bones would begin to heal, although even after the foot bones had healed they were prone to re-breaking repeatedly, especially when the girl was in her teens and her feet were still soft.
Split into simpler sentences: However, as the girl grew older, the bones would begin to heal. Even after the foot bones had healed, they were prone to re-breaking repeatedly, especially when the girl was in her teenage years and her feet were still soft.