The baby will take time adjusting to the solids. Keep trying in small potions and feed her when she is really hungry. Try with grated fruits or mashed potato or banana. And then move on to other cereals. Otherwise, also you should feed kids cereals only when they turn one, as little babies do not have an enzyme that is responsible for helping in digestion of cereals.
https://scienceofmom.com/2013/11/08/amylase-in-infancy-can-babies-digest-starch/
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