Toughen up; act like a proper woman. The female equivalent of "grow some balls".
Example 1:-

Girlfriend: "We're going dress shopping."
Boyfriend: "No."
Girlfriend: "Grow some boobs!"

Example 2:-

Kate: "Hey Sally, how about you ask out Peter?"
Sally: "Nah, I'm too shy."
Kate: "Grow some boobs, Sally!"
by Schloshiy May 25, 2012
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