。
She is a deeply humane person.
Literal
She [topic-は] humanity [in-に] is-rich.
The pattern ~に富む (とむ, 'to be rich in') is a set expression for abstract qualities — 才能に富む ('rich in talent'), 経験に富む ('rich in experience'). It's more formal and literary than simply saying ある ('to have'). Here, 人間性 (にんげんせい) means 'humanity' or 'humaneness' — the quality of being deeply compassionate and understanding toward others.