Have you cleaned the nail thoroughly prior to applying the nail? You need to remove the natural oil from the nail. Are the nails perefectly dry? After filing, have you removed all of the excess dust with a good brush? Is your primer too old?
Also, it depends on how much the client uses her hands. Excess washing of dishes, heavy cleaning and daily typing can put pressure on the nails
Have you made sure the cuticles are pushed back? if products have been overlayed onto the skin/cuticle the natural oils in the skin will lift the products.