。
She's pushing thirty-five.
Literal
She [topic-は] [soon-そろそろ] 35 years-old is.
そろそろ ('soon, before long, gradually') is one of Japanese's wonderful aspectual adverbs — it marks something as approaching or imminent, often with a sense of 'time to' or 'about to.' Common collocations: そろそろ帰ろう ('let's head home soon'), そろそろ寝る時間 ('about time to sleep'). Used with 年齢 ('age') here, it gives 'approaching 35,' the kind of casual aging-marker phrase. 歳 is the standard age counter; the casual variant 才 also appears in informal writing. The plain copula だ keeps the sentence conversational.