。
A good daughter grows into a good wife.
Literal
Good daughter [topic-は] good wife [to-に] becomes [nominal-もの-copula-だ].
~ものだ ('it's (just) the way things are, that's how it is') is a philosophical/generalizing sentence ender. Used for observations about universal tendencies or natural laws. 娘 ('daughter') becoming 妻 ('wife') reflects a traditional observation — culturally dated, but linguistically standard.