I completely disagree with you. Life goes on even after the death of someone close. Everyone has needs, and sex is a need, just like food and water. The elf is a vulnerable person, and if she is told the truth, she will not stand it and will kill herself. And if a guy and a girl want sex, is that bad? Even in times of war, people had sex when they killed people because they loved each other. The protagonist didn't do anything wrong, he just didn't tell the truth to save the elf. He saves her. And the fact that there is a spark between him and elf is not bad. These are mutual feelings. But if our main character killed her mother himself, and then had sex with an elf, then that would be bad. But he didn't kill her mother. He wanted to save her.
I will calm you down. The story with the elf is not over yet. There will be 1 quest, and after it there will be sex.