It's never established that there's a fairy godmother for each being. Nor that a fairy godmother can't help more than one being. It's more likely than, since CINDERELLA got her happy ending, THE FAIRY GODMOTHER stayed around to see if anyone else needed help (which would explain her being in the castle just to tell stories, and in the anniversary celebration in the third movie). And she probably felt that JAQ deserved it after also helping CINDERELLA many times.
