First, call your vet. But if they don’t answer, and since you don’t know the exact amount of chocolate a dog her size can tolerate, here’s how you get it out of her. Force hydrogen peroxide down her throat. That means, take a medicine giver (for people), fill it up with hydrogen peroxide, and holding her mouth closed, insert it into the flabby skin of the lips at the back of her mouth. Hold her nose pointing up, and squeeze it into her mouth. It will run down her throat. Stroke her throat, and make her swallow it.
Do this over and over and over. Soon she will start to heave and bring it back up, along with the chocolate. Keep doing it, until the vomit runs clear. Obviously, this is going to be MESSY, and it will take a LONG TIME.
Make sure you have plenty of towels and someone to help you. Don’t wear nice clothes.
Or you can wait and see. I had a dauschund dog that ate a box of chocolates, and other than throwing up all over, she was fine. And I had another dog that died from eating chocolate, even though we did the hydrogen peroxide thing with him. Hope this helps.