She was born with the potential to /be/ a Sorceress, sure--that much we can go ahead and agree to. But Rinoa wasn't born a Sorceress any more than Edea was--though she still is one, now. ...and, of course, to be redundant, there was no need for Rinoa to /do/ anything about Time Compression--without Ultimecia's power to keep it going, time moved back on its own.