Yeah, its weird, Christie. I'm not sure why this was so challenging. What I did was (per puppy class) put a treat under her nose and draw it down to the ground. That didn't really work, so the teacher said to also push down between her shoulder blades. That, of course, made her lower, but she didn't follow the command without being pushed down.
Finally, I decided that instead of making her "sit" for meals, I'd make her "lay" for them. That worked! I give the command, "lay" before dinner and she does it. So, it's basically bribery:"Lay, or you don't eat."
Actually, today she had me cracking up. She was throwing herself into the floor, hopping up, throwing herself down again, up again, down again...she did it like 6 times in a row. It was freaking hilarious!!! I ran to get my phone, but then she stayed down. Man, that was funny, I'm sorry I didn't get it on film.