How does Judith Loftus figure out Huck's disguise?

Huck becomes nervous at this news and picks up a needle and thread. He does such a poor job of threading the needle that the woman gets suspicious of his gender. Without Huck knowing he is being tested, the woman has him throw a piece of lead at a rat in order to judge his aim. Afterwards, she reveals where Huck went wrong with his "girl" behavior and asks him what his real name is, telling him to be honest. Huck cleverly pretends to be an escaped apprentice hiding in women's clothes to avoid detection.