M.P.
Often babies cry and suffer when their parents leave them because they pick up on their anxiety about leaving them. By now you probably have a lot of anxiety. Is Grandmother anxious? If you could be calm and matter of fact that might help. A definite routine might help.
Does her grandmother hold her and do things to comfort her? "Wearing" the baby could be very good. It sounds to me that she might want more physical closeness to make up for not having you there.
How does she act with her grandmother when you're visiting? Could there be a "poor fit?" Perhaps she'll act differently with a different personality.