Objects:

Practice getting her used to your being close to her while she has a bone or some other valuable object. Hold a special bone or object and offer it to her, allowing her to take it but don’t let go of it. Allow her to chew it for awhile, then offer her a special treat (it has to be very special), while you say “ thank you”. Withdraw the bone while she is chewing the treat. She does not get the bone again until she sits, and lays down. Then repeat the whole process. If she decides the treat you’re using is not worth exchanging the bone for, just use something even better . The goal: to have her think that giving an object up does not mean she’ll never get it back; she will be getting a treat, and eventually be getting the bone back, too.

Make sure you are puppy proofing as much as possible- avoid all situations that make her possessive, until you are ready to set her up.
If she has a possessive episode, use the throw chain as a correction and after you get the object away, ignore her completely (no eye contact, petting, talking: cold shoulder) for a while until she starts to wonder what’s happening and comes to ask for attention. Ask her to sit before she gets attention. Make it short. You want her to crave your interaction. This puts you in a higher position (dominant).
When she is coming to you for attention and sitting to ask for it reliably, start the next phase. Put her in a situation where she is alone with a bone. Leave the room. (If her possessive trigger starts when you come over to her while she’s with a bone, you must be ready to predict that moment.) Set her up to think you’re coming over. The second she normally starts clutching it is the second you will clap once, and bounce a ball or squeak a toy, give very happy praise and make a big party out of it. Don’t wait until she is growling and snapping = too late. You will keep practicing this with the goal of making her react happily BEFORE the hand clap. You will be trying to reprogram her to think of your coming over as a happy thing. This has to be done constantly and consistently to get that reaction.

Food:

Hold her bowl while she is eating. Offer her a treat while saying “thank you”. When she eats the treat, take the bowl away and make her sit again. Hold the bowl for her again. Do this over and over until she gets excited at the thought of you taking her bowl away.
Next step: Hold the bowl on your lap while she sits and waits. She can eat from the bowl- just keep holding it with your hand and keep it in your lap. Offer her a treat while saying “thank you”. She should know it by this point. Instead of giving her the treat, put your hand in the bowl and leave the treat in there before taking your hand away. After sitting, she can get the treat out of the bowl on your lap. You want her to look forward to you putting your hand in her bowl because she will get a really great treat if you do that. Remember: you don’t want to surprise her at first. That’s why you are telling her “thank you”, to get her ready for this to happen.
Have her sit while you “prepare” her food. Put one piece of kibble in the bowl and put it on the floor. Casually walk away and keep busy. Wait until she begs for more and pick up the bowl. Give her one more kibble and let her sit for it before putting the bowl on the floor. Repeat this process. This gets her used to handling her bowl- she thinks it will get her more food each time anybody touches her bowl. She ends up asking you to go to her bowl = non-threatening food contact.
After that, have her eat while people walk past her. You will be right there ready to give her a bit of wet food from a spoon as they walk by. You want her to associate people passing her with more food, making her happy and not challenged by them. Try to change her perception of being bothered while eating.