You mentioned that Plum is loyal to the Queen and the royal family, does that mean Asgore, Asriel and the Adoptees(MK,Chara,Frisk)?
In the AU I use—which I call Swaptwistfell—Asgore is dead and has returned as Flowey, Asriel has rebelled against his mother and now resides in the Ruins in protest of her tyranny, and the children are either dead or would not be adopted by Tori.
This is a Fell ‘verse. In particular, it’s a Fell-verse getting worse with every passing day. The ending where Cash is left alone in the Judgment Hall as the lone survivor is probably the “good” end to this AU. These people either do not deserve to make it to the surface, or they die trying to get the Fallen Child back home.
Make no mistake, Plum and Toriel are bad guys, and they are not the kind that can be redeemed.