。
She's the very picture of health.
Literal
She [topic-は] health itself is.
[N]+そのもの ('X itself / X embodied') is a compact way of saying someone or something is the essence or platonic form of a quality. 'She is health itself' frames her as not just healthy but the embodiment of the concept. Common in admiring descriptions: 美そのもの ('beauty itself'), 真実そのもの ('truth itself'), 悪魔そのもの ('the very devil'). The same structure with 自体 (~自体) is a slightly more analytical 'X considered in its own right.' Modern writing usually renders その物 as そのもの in kana.