Thanks for consulting us.
I think your wife's doctor has not given her birth control pill for the purpose of contraception ( if she is aware of her sterilization
, rather she/ he wishes to decrease her period pain. This is one of the non-contraceptive
indication of birth control pills.
This is true that pills increase the relative risk
& breast cancer
, but the actual risk is very small. Sometimes benefits are more than the risks.
If you want to avoid use of these pills, discuss with your doctor, there are other options like surgery & Hormone releasing intra-uterine systems ( which have very less effects on other organs). You can opt what ever suits your wife best.