Since the problem only asks for the difference in the \(y \)-coordinates, we can ignore the \(x\)-coordinates.
They originally agreed to meet at the midpoint of \((5,-11)\) and \((-7,13)\), so the -coordinate of the planned location is \( \frac{-11+13}{2}=1\).
The correct meeting location should be at the midpoint of \((5,-11)\) and \((-5,5)\), so the -coordinate should be at \(\frac{-11+5}{2}=-3\). The positive difference is \(1-(-3)=\boxed{4}\).
Alternatively, notice that an 8-unit change in the y-coordinate of Barbara's location resulted in a 4-unit change in the midpoint since the 8 gets divided by 2. \(\frac{-11+5}{2}=\frac{-11+13}{2}-\frac{8}{2}=1-\boxed{4}\).
+20 