Chocolate itself is fine -- not all chocolate has milk in it. If you want hot cocoa, you can make it from regular baking cocoa. There's a recipe right on the side.
Pure cocoa is fine- I have dairy/soy/gluten free brownie mix that DD does just fine w/ when I eat it. They're not half bad either! Plus, I found chocolate almond milk the other day which is quite tasty!
Re: dairy free ? - cocoa?
cocoa is chocolate... it's what chocolate is made from...
but honestly, I don't see what harm a cup of hot cocoa could do...