。
She is famous as a soprano singer.
Literal
She [topic-は] soprano singer [as-として] famous is.
~として is the go-to grammar for assigning a role, status, or capacity to someone — here, the role under which the person is known. Western classical voice types entered Japanese as Italian loanwords (ソプラノ, アルト, テノール, バス) when opera and choral music were imported during the Meiji era; the native lexicon never bothered to coin equivalents. Note how the loanword sits directly before 歌手 ('singer') as a category specifier, no particle needed — Japanese is happy to stack noun + noun this way. The plain copula だ keeps it neutral, the kind of phrasing you would expect in a biographical blurb.