[MY OSCAR]

Well , i do not have any experience with this as my boy oscar is a little
pig and will eat anything but i do have a suggestion.
You mention that bella is a shy eater.
Maybe you could set up a crate for her in a seperate room when it is her mealtime take her in her room just place her food dish in her crate but do not put her in too just show her the food and then leave the room. See if that helps. Maybe she is too nervous to eat with anyone around.
also , has she been eating the same food all her life?
if not maybe she has developed a picky eater habit.
if possible get some samples of small breed kibbles and see if there is a paticular one she really enjoys..
Hope this helps , good luck.