Okay, obvious lore drop is obvious. Lets talk about teasing memories from the shrine option. What will it give us? Lore, probably lots of cool lore about the region and of Hui messing things up that didn't need to be messed up. What will the answer we get from it? That some nobles are very bad and neglectful and that's why Su Ling mom is able to still run around. It sounds like she popped up under Hui rule and just hasn't been a big enough problem for people to take care of. Will this give Su Ling the answer she's looking for? Probably not but it will be an answer.
Now, dream fox kid. Who are they? Why are they here? I can see them being one of three things. The most unlikely is Su Ling half sister or some sort of related spirit. Not a whole lot pointing to that being the case besides fox spirit looks and in the same general area. The more likely option I think is that it's an expression of Su Ling's inner spirit blood or something like that. It's the liminal realm weird things happen and what better and weird way to get to the root of your problem than talking with what you believe the problem to be yeah? But the most likely option in my opinion is that it's actually a memory of the shrine's old deity and also Su Ling's mom!
Here's what I think happened. Baron of the land is taking care of it, dealing with problems, worshipping fox spirit and all's good. Then your boss comes around and tells you to poison the land/people for 10 years so they can be relocated and to get them to stop worshipping the local spirits in such barbaric ways. You don't want to die or worse so you gotta do what you gotta do. Poison the land and when the fox spirit gets all up in your business about it you have to kill them. You move your people and tell them fox spirits are evil now. Some time passes and a new fox spirit coalesces from the remains of the old fox spirit because the rulers of the land were cheap and didn't properly disperse the energies. Being a new spirit still figuring out what everything is you only know that this is your shrine and there should be people here, so you turn yourself into looking like a person and go find them but when you do find them there all angry about you poisoning the land and drive you away.
Basically what I'm saying is, we got the first part of the story from the sludge in the shrine, we're going to get the rest of it from a first hand retelling if we go after the fox girl.
[X] Check up on the Kid, if they are up to something, better to know.
[X] Sneak up on the Kid, show them why you don't try and spook a stealth cultivator.
End Crazy theory rant