[matese]

Train the STAY command and use hand signal with verbal command. When she learns the stay command use it when you are eating. Teaching dogs commands must be a routine, meaning, once the dog knows the command it must be used daily. In my house 8PM is treat time, YT has taught me
"nothing in life is free" so Cody has to work for his treat. I put him through every command using verbal and hand signal and every trick also verbal and hand signal, then he gets his treat. I mix the commands and the tricks.
As for your baby laying down when you say sit. Teach her command word UP. Have her lay down, give command word UP also using hand signal, when she knows the up command you can use it when you say sit and she lays down. Cody was laying down when he was to sit, I trained the UP command and used it when he laid down instead of sitting. Your baby maybe confused with her command words. Work with her for 5 to 7 minutes throughout the day,a few commands at a time. Do not have her sit, then ask her to lay down keep the two separated,that is how I trained Cody. Have lots of patience, praise like crazy when she gets it right and give treats. Good luck.