If a woman took the RU-486 pill within hours of a rape, must she go to confession for an abortion considering she had no way of knowing if there was a pregnancy and would not make the same choice again?
Objectively speaking, it would be grave matter for a woman to take RU-486 following a rape because the purpose of the drug is abortifacient. However, mortal sin also requires full knowledge and full and free consent to the action. It is very possible that the psychological trauma surrounding the rape could mitigate against a woman’s full knowledge of what she was doing and/or her full and free consent to the action. If so, if there were sin it would be venial at most.
That said, even if the sin were not mortal due to lack of full knowledge and/or lack of full and free consent, sacramental confession of the action could well be recommended because the grace of absolution can be of assistance to the healing process. The Church does not require the confession of venial sins, but it does recommend it (cf. CCC 1458).