。
She seemed healthier than before.
Literal
She [topic-は] before [than-より] well [seemed-そうだった].
~そうだ (appearance) attached to an adjective stem expresses how something looks — 元気そう means 'seems well/healthy.' The past form そうだった ('seemed') indicates the impression was registered at a past moment. Combined with より (than), the sentence compares her apparent state to an earlier time. Don't confuse this appearance ~そうだ (attached to stems: 元気そう) with the hearsay ~そうだ (attached to plain forms: 元気だそうだ), which means 'I heard that.'