She could not escort him back to his room because in his drowsiness he was still conscious enough to stop her from approaching him. And she did not insist on that. She just stayed in the gazebo where the dinner took place, watching his back getting further and further away.
It was just like what her mother had predicted: that he would refuse her offer of a helping hand. And their plan was made based on this obvious prediction.
They just needed the potion to take effect. When he slept deep and soundly, she would come to his room to accompany him, sharing a bed and spending the night with him.
When he woke up later, he would highly likely be furious at her. But she had been kind enough to him to choose this method instead of her mother's initial plan.
She strongly declined her mother's idea to use an aphrodisiac on him. It was not because she was a tolerant person but because she did not want to hurt the baby in her womb.
