Nurse: Your love says, like an honest gentleman, and a courteous, and a kind, and a handsome, and, I warrant, a virtuous,—Where is your mother?
Juliet: Where is my mother! why, she is within;
Where should she be? How oddly thou repliest:
'Your love says, like an honest gentleman,
Where is your mother?'
The above exchange is the missing part of the question.
The nurse's question foreshadows that what the nurse is about to share may have very serious consequences.
That is why what she will tell Juliet must be between just the two of them.