It seems that the holy old woman that the Princess referred was actually a man in disguise, the brother of the Maghrebi whom Aladdin had exterminated. He resembles his brother and is more treacherous and knowledgeable in magic. He learned about his brother's death and came to seek revenge on Aladdin by disguising himself as an old saint and infiltrating the palace.
The proverb "the younger brother of the dog is more filthy than its elder" is quite true, and this new enemy is even more dangerous than his older brother.