Hi Andre - Estrogen does a lot of good for women - strengthens bones, prevents mood swings and hot flashes, keeps you feeling young. The one bad thing it does is increase your risk for breast cancer. So it's a decision we all have to make: Do I want to put myself at greater risk for breast cancer, vs. the good things estrogen does for me? There's no telling exactly how much greater your girlfriend's risk is at this point; just that it's been increased, and will continue to increase so long as she takes estrogen. For specifics about her own personal risk, she'd need to ask her doctor. Hope this helps - PJH