Well, she certainly must have received the sorceress powers in the auditorium, but it's of course arguable when she 'became a sorceress', depending on what definitions we're using. IF we're saying you're a sorceress the moment you get the powers, then Rinoa was one already in the auditorium. But if we're saying it takes some time, she didn't become one until the space station(or in outer space, whichever).

I mean, the coma time might have been her body adapting to the new powers, making her sorceress only after she was fully adapted. Who knows?