IUD's are a great form of birth control in this situation, but as a heads up, you or your wife should read up on the insertion process and the amount of pain it can cause. If you decide to go this route, advocate strongly for this young women and make sure the medical provider takes appropriate measures. It is often traumatizing for adult women, and in this young ladies current situation, the experience could be devastating. As in, she might avoid reproductive health care for a long time because of it.