I have a shitzu and she's 24 weeks old and she's losing her hair ?????

She seems sick at times ,she only eats when she want's we just love her she's very much part of our family. When we first got her she had a full head of hair i don't know whats wrong with her and the lady breeds mom,dad,sister and brothers which is not right i don't think to do and she sent me chicken liver to feed her not puppy food so it has taken us forever to get her to eat . But i still don't think she eats right now she is losing her hair can someone please give me answers????HELP Thank You(Maddie)