It was too tiring and painful to get married to a person one did not love and then live together for a lifetime. So, she simply did not understand why Shen Yunya used every possible means to get her Imperial Brother.
She felt that true love simply meant one must let go, and not use her love to bind the two of them. It was too exhausting.
"No. Either you get married or, as your brother, I'll kill him!" Xi Jin strongly refused to accept this. He was most well aware of Lin'er's character. It would not be possible for her to let that man have his way with her if she did not like him, let alone giving birth to the other person's child.
In short, Lin'er would be wronged in this matter!
Dongshu Nation's popular customs were not as liberal as Xi Yuan Nation. It was still wrong to lose one's virginity before marriage, and, on top of that, getting pregnant out of wedlock. Otherwise, he would not have used this method to plot against Shen Yunya.