The doctor will have prescribed a form of birth control, either tablets, the injection, the implant or an IUD. Birth control is used to prevent unwanted pregnancies and comes in different types as listed above. If Rita wanted to make sure she would definitely never get pregnant again she could choose to be sterilized or have a hysterectomy.
I dont whether it is true that chemicals are more diluted in present day but whether diluted or not it is still hazardous to your health and it is extremely dangerous to eat close to chemicals.
You want to avoid doing D at all cost. It's important that your friend doesn't feel that your friendship is in danger. That may only encourage her to enduce more self harm.