Thanks for the chapter!
I call shenanigans. This is just my opinion but considering how MC is acting off character I'd say that the operation was very, if not completely, successful. She's too calm about failing and would be frantically studying or contacting Grandfather Yao for alternative measures even if chances are slim. Also, although there were rumors going around saying 9th prince is unable to have children he insisted that there is nothing wrong with his manhood only to MC so my guess is that they're pretending operation failed to fool enemies like the 3rd prince to help prevent another ambush until he's can defend himself better. Obvious Emperor still favors him as MC noted how he was awarding her stuff that would become 9th prince's as well when they married. Speaking of the Emperor, considering what he did to Concubine Bu over wrecking a meeting with Concubine Yue I'd say Yao being exiled for failing to save the life of a concubine is an excuse to cover something else up. Otherwise with his temper the Emperor would've done some physical damage personally and done more than just exile. This is just a hypothesis so until subject comes up or Yao returns or both won't be able to tell wrong or right until then.
As for Quinshuang I agree with MC that she's too suspicious. Granted timing was really early as MC hadn't made too many big waves when first hired but eavesdropping, not spilling the soup despite being startled, and her reaction to MC saying hadn't been able to return Phoenix hairpin is more like a spy with another master and less like a loyal servant. Although that's just my opinion but if she is a plant than likely going to try to take the Phoenix hairpin MC is baiting her with. After all, considering the Emperor's test and issues if lost it the MC wouldn't carry it around or store it in her mansion but in a specific place in her space where no thief would be able to get near it while allowing her access to it at any time.
