Qiu Qiu's cruel treatment and death in the end was such an unexpected event compared to the relatively happy mood of the beginning of the novel. After Grandmistress Qian reincarnates, the happy end Qiu Qiu seeks is ultimately replaced with paying the price of her actions from the previous life.

Qiu Qiu is sent to relive her actions in her previous life and finds that nothing she does will change anything. When she returns, the Grandmistress has reincarnated and now mistrusts her. Even as Qiu Qiu is slowly dying, the Grandmistress is not open with showing affection and even ignores Qiu Qiu for periods of time.

Though the Grandmistress loves Qiu Qiu, the hatred she has towards her for betraying her in their previous love has clouded her judgement. She cannot trust nor forgive Qiu Qiu for killing her friends and loved ones, but neither can she bring herself to kill the other. It's apparent, however, that the Grandmistress does love Qiu Qiu very, very much, going so far to kill herself as well after Qiu Qiu dies.

I think what is most unfortunate is that the Grandmistress in the second life, after getting her soul from the first life, was no longer aware of what QQ has become like now in the second life. Her memories of QQ are all from the first life and so she only remembers hatred and betrayal. A real pity that the 2 of them have now "switched sides". A tragedy that in both lifetimes, one will hate while the other loves, and vice versa. Things might have been different if Grandmistress' soul did not change halfway through. But because it did, it looks like they were destined to always have bad endings. QQ gets like ONE YEAR with the grandmistress to live (slightly) happily before she succumbs to her illness and dies.

I think the point of no return was when grandmistress' soul had JUST switched and she didn't know what this second life QQ was like, and immediately assumed she had betrayed her again, and pushed her to the enemies and then left, thereby creating the chain of events that would eventually lead to QQ's death. And after QQ had returned to the clan barely alive, even if grandmistress hadn't ignored her for several months after and had instead changed her mind and forgave her, I don't think it would have changed the ending because QQ would have died anyway. The moment grandmistress' soul was switched, I think they were inevitably headed for a tragic ending.

After that measly one year that she has left where she's living but not really, the grandmistress basically kills herself after QQ's death in the second life. The ending scene is the grandmistress waking up some time in the past before they meet, but it is unknown whether this is a new reincarnation or the first or second world/life. I guess it's meant to be open-ended and you can think what you like.

The nice thing about the way tragedies are defined in NovelUpdates is that they can have semi-happy endings. And this is one such tragedy: exact details in the last spoiler.

In the last scene, the titular mistress commits su*cide after Qiu Qiu passes away. However, there is a tiny epilogue where she once again wakes up in the past, sees a flower that Qiu Qiu once gave her, and smiles. The smile's meaning can be debated.

Spoiler!!!

The ending made me nearly cry my eyes out but I was also a little confused after the teary bit, because it was google translation. Basically, the part that makes you all heart wrenched, there's one final part that ends the story. I can't tell what that final part is because the Chinese translation by google is literally you doing a lot of guess-work. I think it might be a happy ending and maybe the translation is Qiu Qiu (at least I'm hoping) so one more final rebirth (it would make my tears dry up if this is true). The way it's written about the when reaching 100th something then you'll reach rebirth ad about the rebirth tree essence still being around so I'm guessing they both rebirthed and ended up together. But like I said, the translation makes it hard to tell. It's either the grandmaster rebirth and talked to Qiu Qiu with a smile or the Grandmaster reached the 100th demon level died and came back and is talking to a servent but Qiu Qiu is still gone. I don't think it's the second one though.