She has a craniopharyngioma, the most common childhood supratentorial tumor which is derived from remnants of Rathke's pouch (FA2020 p528). Craniopharyngiomas commonly have calcification and can cause hypopituitary issues (like low HGH). Suprasellar is also the location of the pituitary, and pituitary tumors in general cause bitemporal hemianopsia due to compression of the optic chiasm.
Rathke's pouch (where craniopharyngiomas and anterior pituitary are derived from) is derived from the surface ectoderm of the oral cavity.
Note that the neurohypophysis (posterior pituitary) is derived from neural ectoderm while the adenohypophysis (anterior pituitary) is derived from surface ectoderm of the oral cavity.