Cream cheese can be fed to Chihuahuas in small amounts, although with this food it would be unusual to eat a large quality. A small 1.5 ounce serving has less than 1 gram of lactose so blending some into food to either add flavor or moisture is perfectly fine.
While any food is not good if given in excess, offering small pieces of cheese to a Chihuahua can be a healthy part of a diverse diet. If an owner were to give their dog large amounts of cheese, as with any milk-based food, it would cause diarrhea, stomach upset and possibly vomiting.
For those that have to give their dog medicine in pill form, hiding it in a piece of cheese can often work well, particularly if you use a softer cheese that can be formed around the pill.