I think that is common with betta so dont worry my fish does that some times
my fish does the same thing... but sometimes he eats it off the bottom... but whenever i clean his jar i make sure to get as much of his leftovers as possible ... :)
My Fish spits out the food he doesnt like just like yours did. I feed my fish a sort of flake, wich allows the food to float for much longer as my fish does not eat food at the bottom of the jar. However, i did an experiment by not feeding my fish for three days and as a result, DJ (my fish) was forced to eat the fish food which had sunk to the bottom of the jar.
Same here! My fish does exactly that with certain types of food. He does not eat off the floor of the tank at all. I have found food which he does not spit out though=) so he is a happy little fishy now with his current food.