8 Yr old girl, just diagnosed with ASD, stealing food

Another really important thing came to mind. 

Our biology requires a set amount of nutrients - vitamins, enzymes and minerals, which are found in foods. I want to specify I'm not referring to a type of 'diet' but the chemical make up of things which the human body can digest. 

If your daughter has only been able to previously get the nutrients contained in milk from milk, then her biology might only recall Milk is the source of the nutrients milk will provide: Protein, enzymes, calcium. Here's the catch: These things do not exist in a "milk alternative". I'll make an analogy: If a person eats a good deal of bananas, they may not ever crave potatoes as these food items contain a similar amount of potassium and the human body won't create a craving for this mineral as our very cells don't wish to overdose. Now, you might be craving potato crisps due to the salt content, as your body might be lacking other minerals to help stay hydrated, then perhaps salted nuts sound good as well. 

Humans who steal are either in a state of desperation or deeply sadistic: drug addicts and corporate overlords or tyrants. I would suggest your daughter is too young to be either, rather, just being human and feeling she has to take matters in to her own hands in order to deal with a natural biological process.

From what I've read, one can substitute blueberries and fish for milk to get the same nutrients. I might suggest even buying lactose-free butter, cheese and whole milk yogurt. And then, I would eat how she eats for a few months or longer, so you can gauge if the substitutions are working. If you still have a craving for milk from whatever food sources you've switched to (I might be careful with cruciferous veg for young humans), then it may be time to invest in a dietician to find out what contains the same nutrients (Not what substitute 'works' on cereal). Soya milk will the protein and enzymes even if it's fortified. But it shouldn't hurt you in the least to go without lactose for any length of time. 

Another really important thing came to mind. 

Our biology requires a set amount of nutrients - vitamins, enzymes and minerals, which are found in foods. I want to specify I'm not referring to a type of 'diet' but the chemical make up of things which the human body can digest. 

If your daughter has only been able to previously get the nutrients contained in milk from milk, then her biology might only recall Milk is the source of the nutrients milk will provide: Protein, enzymes, calcium. Here's the catch: These things do not exist in a "milk alternative". I'll make an analogy: If a person eats a good deal of bananas, they may not ever crave potatoes as these food items contain a similar amount of potassium and the human body won't create a craving for this mineral as our very cells don't wish to overdose. Now, you might be craving potato crisps due to the salt content, as your body might be lacking other minerals to help stay hydrated, then perhaps salted nuts sound good as well. 

Humans who steal are either in a state of desperation or deeply sadistic: drug addicts and corporate overlords or tyrants. I would suggest your daughter is too young to be either, rather, just being human and feeling she has to take matters in to her own hands in order to deal with a natural biological process.

From what I've read, one can substitute blueberries and fish for milk to get the same nutrients. I might suggest even buying lactose-free butter, cheese and whole milk yogurt. And then, I would eat how she eats for a few months or longer, so you can gauge if the substitutions are working. If you still have a craving for milk from whatever food sources you've switched to (I might be careful with cruciferous veg for young humans), then it may be time to invest in a dietician to find out what contains the same nutrients (Not what substitute 'works' on cereal). Soya milk will the protein and enzymes even if it's fortified. But it shouldn't hurt you in the least to go without lactose for any length of time.