As you said your female boss is sexually exploiting you on the pretext of promotion then you should immediately take action against her. You can’t let her exploit you because you want a promotion. She has no right to prevent you from getting a promotion if you have legally earned it. Entertaining her or bearing her exploitations is wrong and it won’t be good for you too. She might take you for granted and will continue to exploit you in the future. You should strictly tell her that you are not comfortable with this and she should stop doing that.