What is she doing???

I have an extremly challenging 4.5yr old, she will be 5 in september.
I believe she has ODD (oppositional defiant disorder), i have done so much research on this and am getting a referall to see a peadiatritian on friday..anyway

I had a little boy 5 weeks ago and now he is suffering her "attacks" about 30min ago I couldnt believe it I only walked out for 1 min to put the kettle on
come back and i sat down to talk to him (he in bouncer) and i could smell something so i asked her if she fed him and she said no,(she was eating a snack called noodle nuggets) then i seen crumbs on his growsuit and he poked out his tounge and there was food all over it, so i spent 10min scraping noodle nugget crumbs out of his mouth, then after id gotten them all he threw up what he had swallowed.
I asked her "are you trying to hurt your brother" she just shrugged her shoulders with a smug look on her face and walked to her room.
I have tried reasoning with her, talking to her, not yelling at her, yelling at her, i dunno what else to do short of smacking, which i hate.

i dont know what else to try.

DO u have or know anyone who has a child with ODD, or can u offer some advice?

My best friend has a step-son with ODD and he did a similar thing with his baby sister and nuts! I know that she has had him assessed by a paediatric psychologist at the Royal Children's. She is also looking at putting him in a specialist school in Glen Waverley that deals with kids with these issues.

ok great thanks, what kind of school is it?

I'm not sure but can find out for you. She did say that the class sizes were only 6 in a class.

That'd be great, im not sure we have schools like that, we do have a "special" school but its for children with physical disorders

It's the Cheshire School and it runs the Best Chance Early Chilhodd Intervention.