My first afib episode occurred one month after hysterectomy for uterine cancer. I'm 51. I do not know all the biophysiology of this, but hormonal changes due to "surgical menopause" can be a trigger for afib, even in a woman your wife's age, whose ovaries might have still been producing some estrogen.
One thing that might help is for her to use natural progesterone cream. There is convincing evidence that it is a lack of progesterone that leads to gynecological problems in women, not so much estrogen. Supplementing with estrogen or having a condition called "estrogen dominance" can cause more problems, including cancer.
A helpful book on this whole subject is by John R. Lee, M.D., called "What Your Doctor May Not Tell You About Menopause."
For myself I am still trying to figure out all the triggers and causes of my afib, but what I suspect is a combination of adrenal burnout, hormonal imbalances and improper diet, i.e., too many years of eating sugar and dairy products and free glutamates. I think they all tie in with each other.
K