How to stop small dog food aggression over things found on the floor/bed that they shouldn't be eating?

Pick up the things it wants dilligently. Teach "leave it" to prevent it from grabbing things you might have missed. To stop the aggression itself in case you missed something, you have to teach the dog to trade with you. Start very small. Dogs have currency, a hierarchy of how much they like things. Always trade for a higher value reward. You reward the dog for dropping the item without forcing it. Dogs learn to love trading because they get something even better. Look up how to do this and consult a trainer if you run into trouble.

Pick up after yourselves and don't leave food (and other stuff you don't want chewed/eaten) laying around for the dog to get into.

Pizza on the floor? NASTY!

Nothing like setting a dog up to fail - how many dogs are going to pass that up!?

Clean up your rooms and keep the door closed if you don't want her dog getting into stuff. This is a people problem, you need to supervise the dog better. You need to teach them what they can and can not put their mouths on, what is theirs and what is yours in the house.

Look up RESOURCE GUARDING on the internet on how to handle the aggression when the dog takes something it shouldn't.

Tidy away things you dont want the dog to have, they should be out of his reach.

then start a training process to teach him to swap the item he has for something you have. You start off with low value toys and hand them back to him after he has eaten the treat. As time goes on he should become more comfortable with handing over his treasures.

Check out the link for possessive aggression on this website;

http://www.aspca.org/pet-care/dog-care/common-dog-...

Make sure you don`t leave any food (or other stuff) about for them to get aggressive "over". Simple remedy.

Also I hope you feed them separately to prevent any aggression in that department.

NEVER leave anything you don't want eaten where the dog can get it. Train YOURSELF.