The scene fades exactly when she leaves, so there's no way to know if she haven't spoken with an authority of the school to go there and rescue Snape after she left (she was not a prefect)...

It doesn't mean she didn't asked it sometime after or before when her emotions were more composed. And I believe that - for the fact that Snape couldn't tell anyone about Lupin's secret - she didn't have a real notion of the risk Snape passed through in the Shack.

Those are really good points! :) I hadn't thought of that before. Thanks for commenting. How'd you come by my lj blog, if you don't mind my asking?

I'm glad that you like my essay. Thank you very much! :)