What kind of food are you giving may I ask? usually when they are pups and haven't developed their "picky palate" yet LOL (mostly our fault I think!) they will eat anything.
Try sit first. Hold the kibble/treat at nose level and move it back and up over their head. It helps if they are backing up to a wall. They will look at the food and rock backwards, ending in a sit.
Once she gets sit, go for down/lay. In a sit position, move the food down to the ground. many times they are too short and don't understand why to food is on the ground, and they just look down. If this is the case, try the down command on a nice big stool or sofa and move the food below the seat level. If their bum goes up, place your free hand above it, so when the bum goes up, it feels your hand and lays back down.