Is it really possible to have several co-morbid mental disorders?

My goddaughter is sixteen now and has been depressed I believe for many, many years. Last year she was diagnosed with bipolar disorder after the family became very concerned regarding her erratic, disturbing behaviour and had her hospitalized. Around that time she had been diagnosed with bulimia with anorexic tendancies. Things have been up and down with her since then. Although she stopped purging her food issues remain and her bipolar and mental state in general has fluctuated, greatly. She is at the point now where she barely eats, sleeps, leaves her bed or talks to anyone anymore... We are very concerned, as are the doctors. Now they are suggesting she may have somatization disorder, depersonalization disorder and/or anxiety issues. She also has a rare heriditary blood disorder she was diagnosed with years ago but doctors now believe that the symptoms are worsened by psychosomatic factors... Can she really have all these problems? I mean how is it possible?