chin change of behavior

Hi, recently i adopt another chin to accompany my origin chin. My orginal chin changes her attitude toward me. She used to be attracted to treat and i alway uses treat to lure her back to her cage. But now she has no interest to the treat and even bite me when i feed her. I am sure that i do not have the smell of the new chin as i always feed my original chin 1st. The chins are also sperated in different cage. Please advise me what can i do for the current situation. Thanks