1 + cos(t) = 0
cos(t) = -1
t = pi
2 * (1 - cos(t)) - 1 = 0
2 * (1 - cos(t)) = 1
1 - cos(t) = 1/2
1/2 = cos(t)
t = pi/3
This gives us 2 possible angles to check
T = (2/3) * (t + 2 * sqrt(2 + 2cos(t)))
T = (2/3) * (pi + 2 * sqrt(2 + 2 * cos(pi))) , (2/3) * (pi/3 + 2 * sqrt(2 + 2 * cos(pi/3)))
T = (2/3) * (pi + 2 * sqrt(2 - 2)) , (2/3) * (pi/3 + 2 * sqrt(2 + 1))
T = (2/3) * (pi + 2 * 0) , (2/3) * (1/3) * (pi + 6 * sqrt(3))
T = (2pi/3) , (2/9) * (pi + 6 * sqrt(3))
T = 2.0943951023931954923084289221863 , 3.0075327775562348888060714294033
It looks like walking around will take the shortest amount of time. Makes sense, too. The length of the perimeter is 1.57 times the length of the longest distance between the 2 sides and she walks 2 times as fast as she rows. It'd be more advantageous for her to just walk it, even though it's a longer combined distance.