[hammy]

Hello!!!
The chemistry of chocolate is a little complex to go into detail here. But chocolate contains theobromine, and it is this that causes the problems in dogs.
Some dogs are more sensitive to it than others. The toxicity of Theobromine also depends on the amount consumed, i.e. the size of your pet, the type of chocolate, (The darker the chocolate the more toxic) and quantity eaten will determine if, or how toxic it is to your dog.
You don’t say how much she has eaten, if you know what was there. The symptoms of chocolate toxicity are seen as hyperactivity / excitement / nervousness / trembling / vomiting and diarrhea.
So sleeping and lethargy ??. These signs, or some are usually seen within 12 hours of ingestion, so if she ate it last night??? I understand it takes a fair amount to cause a toxic reaction. I would call your vet and ask for some advice, if you become concerned for her.