Use the Pythagorean theorem:
Height is 14, base is 3, so we can calculate the length required.
Length = sqrt(14^2 + 3^2)
Length = sqrt( 196 + 9)
Length = sqrt(205)
Length = 14.32 feet.
The ladder needs to be 14.32 feet. The longest her ladder can be is 14 feet so her ladder won’t work.