。
She is no longer the woman she once was.
Literal
[topic-は] no-longer before [genitive-の] she is-not.
もはや ('no longer, already') is a literary/formal alternative to もう, often paired with negation to express 'no longer' or alone to mean 'already' with a sense of inevitability. 以前の彼女 ('the her of before') is a poetic self-reference — using 彼女 ('she') as a noun to characterize her past self. The whole sentence has a somber, evaluative tone — the kind of line that opens a chapter or summarizes a transformation in a novel.