。
She's about my age, give or take.
Literal
She [topic-は] roughly me [with-と] same age-range is.
年頃 (toshigoro) is the noun form of '(at the) age of, around the age of' — useful for talking about someone's approximate age bracket without naming a number. The same word means 'marriageable age' in older usage and 'adolescence / coming-of-age years' more broadly. だいたい ('roughly, more or less') and 同じ年頃 ('same age range') stack to give a doubly-hedged comparison: not 'same age' but 'about the same general life stage.' The と marks 私 as the comparison standard — 同じ X と Y is 'X is the same as Y.' The comparison structure here is the canonical [A]は[B]と同じ frame.