For those still struggling, Thora is usually down in the lower part of Riften, sat on the docks. The Auction house is the place you need, south of Rorikstead, and youll need to get the ticket from the cart outside, then either win or steal the key to Krossa.

the key is in a big mansion on the road near or beyond the western watchtower of whiterun, regardless of where you are on the quest stage it will automatically trigger the appropriate one. the place is a big auction house with a few ways of getting in and obtaining the key if i remember right

I didn't find the second location you say there is in the messages.

did you get the quest related to this mod?

I arrived at the ruins of Krossa, but the door is closed. I couldn't find the key, which could be a button, a lever, or a secret passage. There was an expedition camp, where there was no one. On the other side some bandits, who ended up dying, as well as a mammoth and some bears. No one with a key.
Some ice dead who didn't have anything interesting either.
I've scoured the entire area around the ruins, which aren't solid, just walls. I managed to climb a leaning pole and saw this.
So the key is a mystery.

if you heard her yelling it could only be due to combat, if it was outside look near the marketplace or maybe even in the cannals underneath

i heard her yelling but i could not find where she is

check the tavern or the main marketplace in the city, as a last ditch effort, the main hall of the jarl's palace

where is Thora in Riften?