According to the official royal website, Charles' titles are: His Royal Highness Prince Charles Philip Arthur George, Prince of Wales, KG, KT, GCB, OM, AK, QSO, PC, ADC, Earl of Chester, Duke of Cornwall, Duke of Rothesay, Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland.
Since the unification of England and Scotland in 1603, the titles have fallen from habitual use, the holder also from then on usually being Duke of Cornwall, Prince of Wales and Duke of Rothesay, which were preferred, and is now seldom referred to, except as the last in the conventional list of the Prince of Wales's titles. Similar to the process of Crown consent (see Royal Assent), in order for any bill affecting, directly or by implication, the personal property or interests of the Prince and Great Steward of Scotland to be heard in Parliament, the Prince must first consent to its hearing.
So - if Charles is Prince of Scotland, than Camilla as his wife is Princess of Scotland.