From my understanding
There are factions inside the palace.
The Peony Faction is lead by that bitch, she had the highest rank of all the noble ladies and seemed to be in the running to be the Queen. So the concubines of the King had two factions.
One that followed the Peony bitch and served her since if she became queen they could be part of her inner circle as ladies in waiting. There's also the fact that she is old noble blood.
The neutral faction was concubines that weren't interested in being queen and just waited to see who would be. But they were being abused by the Peony butch since they didn't side with her or are from new noble families, who gained a title through money and not blood. (I could be wrong about this part)
Diana is from a new noble family, an extremely rich one with alot of influence. So she entered the palace not to be queen but to even the playing field. Diana and her faction outright oppose Peony's faction and even out ranks her since the Prince "favors" her. Since Peony will see her as the biggest threat and gradually ignore the kings true love. So I think Diana is setting everyone to believe the king favors her so much that she will be queen.
When in reality its a cover to protect the low ranking concubine who will be queen.
Also most of the neutral faction has sided with Diana since she protects them from the abuse the Peony did to them in the past.
Also I believe Diana's family and all the new nobles don't want Peony to be queen since she will make life hard for families like them since she believes in noble blood ancestry then money.
I mean I could be wrong im not gonna lie I might have misread some things
I am confused and I don't understand.... Someone please explained to me