After the princess got married, she came back to marry the male protagonist who married the current emperor. The female protagonist was reborn. She knew the outcome of the marriage, but she still went there without hesitation for the sake of the country. Only in this life, she did not have so many regrets.
When you go to the harem, you don't compete for favors, you don't have children, you cling to your thighs and take care of yourself in peace, which makes you stand out among all the palace battles.