中译英：她的梦想是成为一名成功的芭蕾舞演员

Her dream is to become a successful ballet dancer.

Her dream is to become a finest/ successful ballerina

finest: a. 好的,出色的
successful: a. 成功的
ballerina: n. 芭蕾舞女演员

She's dreaming of being a successful ballet dancer.

Becoming a successful ballerina is what she has been dreaming of.