I heard that this girls house caught fire on Xmas! Uhmm... should I do something?

Absolutely. I'm not saying you have to donate any money to the cause or anything, but call her up or send her an email telling her that you are praying for her, or if you're not religious, tell her that she is in your thoughts. Let her know that you know about the situation and feel bad for what happened. Even if you don't like this girl, imagine if it were you who's house burned down. You would want all the help and emotional support you could get! You don't have to magically become friends with her or anything, but be nice. God bless.