。
She's feeling much better than yesterday.
Literal
She [topic-は] yesterday [than-より] much body [genitive-の] condition [subject-が] is-good.
体の具合 ('condition of one's body') is a more body-anchored variant of plain 具合がいい — the の chains 体 ('body') to 具合 to specify physical wellbeing as opposed to mood (気分) or general state. ずっと sharpens the comparison from 'a bit better' to 'much better,' a key intensifier in any comparative expression. The construction lacks an explicit second half (no 今日 'today') — Japanese routinely omits the implied other side of the comparison, leaving the listener to infer 'than yesterday, [today] is better.'