They refused to believe that the princess will become the next queen and instead believed that the Tailor was just praising her in other to get favor from her.
Even if she was not the Queen, she was still the wife of the king to be so a person like a tailor and a servant will give her face. This did not mean that princess Ellen had any real power. Princess Ema and Jane analyze the situation this way.
They put on a fake smile, so what if the servants respect her, she will never get the chance to become the Queen and they were certain that whichever lady became the Queen will be wry of her because of her beautiful face.
If she is lucky the lady will suppress her, if she is not, the Queen will scheme against her. Who knows she might get chased out of the Palace. The more the two thought towards this direction the happier they felt.