Let's denote \( m \) as the amount of ground beef (in pounds) used for each meatball.
Sadie needs enough ground beef for 15 meatballs, which would be \( 15m \), plus 2 pounds for the meatloaf. Therefore, the total amount of ground beef she orders is:
\[ 15m + 2 = 4.25 \]
Now, we can solve for \( m \). First, subtract 2 from both sides of the equation:
\[ 15m = 4.25 - 2 \] \[ 15m = 2.25 \]
Next, divide both sides by 15:
\[ m = \frac{2.25}{15} \]
Calculating \( m \):
\[ m = 0.15 \]
Therefore, the amount of ground beef Sadie should use to make each meatball is
\[ \boxed{0.15} \text{ pounds}. \]