Macadamia Nut Toxicity In Cats? Urgent!?

There were macadamia nut cookies momentarily left unattended, and my cat managed to get a small piece of cookie before I saw her and made her stop. I read on the internet that macadamia nuts are toxic to cats... the small piece she ate was only cookie but I'm pretty sure there are small fragments of nuts mixed in the dough. I'm really nervous because it said I have an hour from the time she ate it to make her throw up. Should I take some kind of action or is the amount she ingested too small to cause harm? She ate a really small piece but I'm not sure exactly how toxic macadamia nuts are.