I'm glad to hear she is eating and drinking and playing as usual, but did settle down to sleep at the appropriate time. Because it was milk chocolate, she seemed to vomit most of it, and she ate about 1/4-1/3 of the 8 oz. bag, she should be alright. It could have been worse if it was dark chocolate and she ingested more.
I hope you received my previous answer, but just in case you haven't, I'll repeat it for you, here:
If your dog is throwing up on her own, that's good, because she will get rid of most of the chocolate, if she ate it a short while ago. Look for the chocolate chips in the vomitus. If it was milk chocolate, regular sized chocolate chips, and half of an 8 oz. bag, she should be evaluated by the vet, ASAP. If she's getting rid of it by vomiting, as I mentioned, that's good, but if she's small and weighs less than 20 lbs. some of the chocolate can be absorbed into her system, and this will cause health problems. You can read more about chocolate toxicity in dogs, here:http://www.petplace.com/dogs/chocolate-toxicity/page1.aspx
If she's showing hyperactivity, increased panting and heart rate, the caffeine and theobromine in the chocolate is adversely affecting her system.
If she's able to keep it down, try feeding her 2 slices of very burned (black) toast, crumbled up. The charcoal from the black part will help to neutralize some of the toxins from the chocolate.
Please try your best to bring her to the ER vet tonight, so she can be evaluated and treated and all the chocolate can be gotten out of her system.
I hope all will be well!
Continue to monitor her, and if all seems well, make sure to keep all chocolate and other dangerous things she could get into, behind closed doors with child locks on them, so there are no more nerve wracking incidents. If she is still vomiting or is not eating, drinking, eliminating or active, as usual, definitely have her seen by the vet, ASAP.
I hope she'll be fine!