Should I be this worried?

My mom has recently lost weight, at first she looked great, perfect after losing 15 pounds. Now she looks unhealthy and way too skinny. She confided in my dad that she went to the Dr. because she is scared because she has a full blown eating disorder. She eats dinner and my dad witnesses it every night, so we are assuming she purges. My dad has never noticed but is now going to pay attention. Today she has been extremely sick and in bed all day, she never gets sick. Do you think this is the flu or a side effect from the eating disorder? I am worried sick, I don't live at home so it's hard for me to monitor her.