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It is definitely possible to train any parakeet - the key is just to be patient. Parakeets can live up to 15 years so you have a lot of time ahead of you to work on it. A one-time issue with grabbing is going to be forgotten over time.
Lots of keets at first only eat seed, so take it slow and easy with other food. Try lettuce - often keets will like to nibble on that!