Have you considered raw goat milk? Unless the allergy is to the casein protein, she should be okay with it. It contains the same amount of fat/nutritional b vitamins as cow, but is actually easier for the body to process because of its smaller molecular structure.
Coconut oil is an excellent source of fat and is high in anti-inflammatory omega 3. Avocado too, as mentioned earlier.
Just to respond to some of the other posters, it is processed grains and sugar that contribute to cholesterol and heart issues, NOT animal fat. The lipid theory is just that, a theory and there is now much scientific evidence to refute it. Grass fed, antibiotic free meat is highly nutritious and there's nothing wrong with butter if there is not an allergy involved in the equation!