As a breast cancer survivor, 2 yrs out, just wanted to add dealing with the dx and treatment is surreal and an emotional roller-coaster for most of us.
There are body issues, side effects from current and ongoing meds related to the breast cancer, not to mention varying degrees of fear, terror, depression, sadness, anger and feelings of loss of the "previous life and health.", all changing day to day or even hour to hour.
So I am just saying, there will probably be alot of ups and downs and you won't always understand why she says or does the things she does. - Most women do associate to some extent their hair and breasts with femininity and attractiveness. It will take time, but you will work together for a "new normal."
The best thing you can do for her is listen to her, be patient and continue to love her. Don't take it personally, if she is angry or sad some days.
Best wishes to you and your wife.
Things will get better in time.