I've had a friend similar to yours, yeah you can encourage them to eat but don't make them feel to bad about it. Just try to be there for them because there might be a reason behind why she isn't eating, you should maybe ask her about it. If it gets really serious you should go to an adult.
The complete blood count (CBC) is a group of tests that evaluate the cells that circulate in blood, including red blood cells (RBCs), white blood cells (WBCs), and platelets (PLTs). The CBC can evaluate your overall health and detect a variety of diseases and conditions, such as infections, anemia and leukemia.