@FTCU
Jing is married . That's why she cannot answer and she had also said in the dragon bone prison that she wants to spend the rest of her life.
YSQ represent the simple life she want hence she answer yes to XL question. YSQ is in a way not married since ffyy did not marry ysq.
When asked about wanting to marry Jing. She is not answering because Jing is married. He is the one she is in love with. She cannot have him.
later on xy marries Jing [( she has now both the man she is in love with ( Jing) with and her want for a simple life (YSQ)] under the moon.
At the end if the story she again Jing/YSQ in from of her the people important to her and get their blessing to have their long life together.
If you noticed he is not even called YSQ by XL.
When jing comes back. From thr dead. Xy call him Jing. To prove that it is really him ( all that he represents to her, Jing them say " I am WXY's YSQ .
I he does not say "i am YSQ" or "I am xy 's YQ".
"Actions speak louder than words" and with XY this saying comes true.
Xl is the one who knows who XY's heart beat for. Thanks to the bug, he has been aware of her deep romantic feelings for Tushan Jing . This since he took the lover bug.
He has shared the joy and pain she has been feeling for Jing. In this he has shared her fate.
This is why he rephrased the question. Xy is stubborn.