If your friend has a leak then there is a higher chance the area that the fluid is leaking from will seal up and fluid levels will build. The bigger concern would be if the fluid is low for another reason and if so why. The chance then of levels increasing would be low. There does need to be a certain Amount of fluid for her baby to be able to develop normally (lungs, kidneys, limps etc) FX the next scan shows an increase in fluid.