、。
She likes jazz, and so do I.
Literal
She [topic-は] jazz [subject-が] like [is-だ] [but-が], I [also-も] [so-そう] [is-だ].
A clean 'me too' construction using そうだ ('it is so') as an anaphoric pro-predicate — referring back to '好きだ' in the first clause. Without 私もそうだ, the speaker would have to repeat 私もジャズが好きだ in full, which is wordier. そう as a pro-form lets Japanese collapse repeated predicates the way English uses 'do' or 'too.' This pattern is one of the most natural ways to express agreement in spoken or written Japanese.