I will do :) lols.

She wouldn't be in the castle for long, just her last few minutes whilst Snow is on her way there...so I think it still could make sense...she just would already be gone, when Snow makes her presence in the castle.

Edit-In which paragraph did you have snow arrive? :) I am thinking if she arrives paragraph 2-3, or the end...then my first paragraph can have Morganna still in the castle and then run the rest of my post...so there'd be a little time skip in mine. So she'd be gone, before Snow gets there in your post.