。
She has completely recovered from her illness.
Literal
She [topic-は] completely illness [from-から] recovered.
すっかり ('completely / entirely / fully') is a 擬態語 for total, thorough completion. Pairs naturally with verbs of change or finishing — すっかり忘れた ('totally forgot'), すっかり変わった ('completely changed'), すっかり大人になった ('grew up entirely'). 回復する ('to recover') takes から for the source state being recovered from, paralleling the English preposition. The Sino-Japanese verb 回復する is the standard medical/everyday word for getting better; 治る is the more colloquial 'be cured / heal'.