It could also have been not a joke.
If she had been reborn with her entire personality intact, she might not have even let Mo Yao follow her in the first place.
Being reborn, she was, to some extent, influenced by the innate kindness amidst social repression within the original Musheng's bones, which is why Shen Nanyi and the others used to say that she and her former self had grown somewhat apart.
K was someone who couldn't take any jokes, not to say he was cold and ruthless, but he certainly didn't always speak with a smile like she does now.
The current Musheng has a lot of K's shadow in her bones, so those who know the truth don't doubt her authenticity, but could it be her personality is now more influenced by the original Musheng?
More approachable?
Different environments forge different personalities.
With this identity, Musheng needed to interact with too many people and things, mostly from the middle stratum of society, so naturally she couldn't be like before.
