Emily - Here are some suggestions on how to work towards resolving agression in your dog. It has little to do with food, lack of exercise, or being in a crate during the day, nor lack of affection, ect. (although all of these can factor into the profile if there is some lack in any of these areas.
Please read this info:
http://www.dogpatch.org/training/aggression.html
I would also suggest you look into getting a copy of any book that addresses behavioral issues in dogs. Even general books about raising a Yorkie or dog will have a chapter on aggression and how to work towards resolving it. You may even want to consult with a trainer for some suggestions, if they are willing. (you may have to pay a consulting fee).
Putting her back in your bed is a big No-No. (so I am glad this is not an option for you).
I think with a little understanding of what's going on and some training techniques, you should have a really great family pet!
Hope this helps!