That would be very frustrating and I am sure that as your friend she did not mean to hurt you. Maybe she thought she could help you make it all go away by saying those words. We all have different genetic make up and some of us are predisposed to certain things. If she had a family history of breast cancer and ended up getting it there is no way anyone would ever think it was all in her head. It is the same thing but unfortunately it is harder to pinpoint a specific diagnosis with mental illness.

I would tell her how you feel rather than have it bother you and keep you angry.