You need to find the explosives and clear out what she did.
First there are hidden areas in the cells, look for I think it was tiny little square buttons on the wood frames around the hidden doors. You need to find the hidden explosives (run on setting

)
First you need to find the hidden key
That prisoner gives you a really good clue as well if you utilize him.
This is from a walkthrough:
-The cell doors open by pressing a button to the left of the locked door
-You can see an obvious secret passage in the cells on the southern wall.
Start from the southeastern cell and toggle a button on the wooden beam on the
left next to the back wall.
-The next button is on the right as you face the other obvious false wall.
This leads you to a key which opens the chest in back, near the explosives.
-Take both explosives. There's more than one passage that needs clearing.
-Past the first cave in, the map shows a secondary cavern branching off of
the main cavern to the west. Use the second barrel of gunpowder to open this
area. You'll find a key at the end.