。
Despite the treatment, she didn't get any better.
Literal
She [topic-は] that treatment [despite-にもかかわらず] not-at-all become-better not-was.
~にもかかわらず ('despite, in spite of') is a formal conjunction — heavier than the casual ~のに ('even though') and more emphatic about the contrast. 少しも~ない ('not at all,' lit. 'not even a little') is a fixed pair-construction for absolute negation. 良くならなかった is the negative past of 良くなる ('become good, improve'); the い-adjective 良い becomes adverbial 良く + なる. The whole captures medical futility — treatment given, no result — and the formality matches the kind of clinical or narrative setting where such language naturally appears.