It would have to be proved. It’s a criminal act, and the perp would and should have to be prosecuted. If you threw out “Oh, I was raped,” as a falsehood to obtain an illegal abortion that is unjustifiable, then that person should be prosecuted for alleging a false crime.
So she would have to prove she was raped. To whom? What panel are you setting up to be the judge of this?
What is the threshold? Prove beyond a reasonable doubt, by the preponderance of the evidence? And would the process be just a traumatic as carrying the child? Actually asking her to go over the details of the incident bit by bit.
I understand the reason why people want to give a exception for rape. I don’t agree with it but I understand it.
I just don’t think it can work practically.