Romeo: Well, in that hit you miss: she’ll not be hit
With Cupid’s arrow; she hath Dian’s wit;
And, in strong proof of chastity well arm’d,
From love’s weak childish bow she lives unharm’d.
She will not stay the siege of loving terms,
Which is the best meaning of the phrase "she’ll not be hit with Cupid’s arrow”?
When Romeo said that she wouldn't be hit with Cupid's arrow, this phrase was referring to,an allusion, how Cupid, the God of Love, didn't hit her with the love arrow. He was saying that Rosaline didn't love him.