Jayme RutledgeMarguerite Robbins with her cattle. Sweat pours down Marguerite's sun-baked face. She feels briars scratching through her dusty jeans. The buzzing and biting of mosquitoes is maddening. So is the old fence lining one of the back pastures. It's broken again. Marguerite stops what she's doing. Why in the heck am I doing this? she asks herself. Running the 142-acre east Texas cattle ranch she owns near Greenville with her husband Doug is back-breaking work. Marguerite, 55,