If the dog is biting this hard, you do need to enlist the services of a certified and reputable behaviorist to walk you through things and be there one on one to observe. Be sure and get someone who uses gentle, positive methods which employ brain over brawn. Be careful who you get.
This is one of aggression problems which, I think has a much better prognosis than some other types.
In the meantime, like Spiritus said, keep your child away from the dog. In addition, while you're looking for a behaviorist, stop using a food bowl and water bowl all together. Put all toys away except when you're working with her. What does your dog know how to do? Sit, down, come, stay? Have her sit and give her a few kibbles from your hand. Walk away, then ask her to come and sit in front of you. Give her a few more or a small handful. Same thing with the water. Put some water in a different vessel, not her regular bowl and ask her to perform some skill and then hold the bowl for her to get a drink. (be careful that you don't forget to give her ample changes to drink throughout the day) It will hard to remember but soon you'll be able to put the water bowl back down for her. So for the time being, you'll have to be very involved with her in this way. When you set out her ration of food, don't go through it all at once, but throughout the day, every hour or so, go through some obedience skills and use the kibble as her reward. Use all motivation and reward methods. Do not put her on the defensive. Put a few higher value treats in your pocket for above and beyond the call of duty good kind of behavior.
So, in other words, she does not own the food. You do. You decide when she gets to have some and she must perform/work for each and every mouthful. No more being reinforced for that defensive biting and snarling because you're going to be regulating her evironment.
When you are ready to work with her with toys, take one out of the drawer (or where ever) and ask her to sit, then heel, down....give her a toy. Take a high value treat from your pocket, (hot dog piece, cheese, fresh meat) and trade her. Then give her back the toy. make this into a game. Encourage her to retrieve. She's a Lab after all. LOL. This is all fun and games. Repeat that, while giving the cue, "give" when she is to put the toy into your opened hand and "take," when you hand her the toy to her mouth. Let her play with it, play fetch with her for a little while, then trade her again and put it away. Session over.
Work on obedience a few times a day for short sessions in addition to freuqent commands during the day. Loose leash walking nicely, sit/stay etc. You can get help here for those things if you need it.
After a couple of weeks of hand feeding, get out a bowl and hold it. Have her sit in front of you or lie down. Put in a handful of kibble and even a chunk of a high value thing like cheese or meat and hold the bowl where she can reach it but hold onto it. If she is not trusting of you at this stage and is nervous, shifty eyed, growly, she is not ready for the bowl. Go back to hand feeding. You don't even have to use a bowl but it keeps your floor cleaner. You can toss a few kibbles on the floor in exchange for a skill. One skill for a few kibbles. When she is seeming to be more "grateful" for her food being given by you, try setting the bowl down on the floor. (I'd use a couple of your bowls, not hers and switch them around for a while.) Or paper plates. Ask for a skill, drop a handful of food in. Feed her invarious locations, not just one place. Drop in a hunk of cheese or something equally good when she seems calm and undefensive. (only) Move the bowl over two feet with your foot (with a cowboy boot on)lol. Be confident and cheerful. Drop in some more. Then drop in another treat, only not from standing but lower your hand closer. Don't be tentative and wishy washy. If you're still having a problem with her, your behaviorist should be on the way by now.
No matter what she likes or wants, (make a list) if she wants to go outside, if she wants attention/affection, if she wants a toy or a stick to be thrown, she needs to earn it. "Do you want to go outside? Sit first. Do you want me to throw the stick? Sit first and wait for a release word." You need to control her resources and she needs to know it. Do not react to her so much. If she does something to elicit your attention, ignore her. You be the one to invite her to come get a pat or scratch behind the ears. Later, way down the road, you can relax that a little bit. It's not natural to not have a two way interaction to some degree IMO. But for now, you're going to give her the cold shoulder just a little. Don't look at her all the time or speak to her much unless you're telling her to sit or that she is being a "good girl." You must reward and reinforce good behavior any chance you get. That is imperative. But what I mean is that senseless idle chit chat that most of us engage in with our dogs. Start making her think in terms of two things only; She performs what you ask and she gets to live. (eat, interact socially, go outside, play) etc.
Your child, if the dog is safe with her at other times, not around food, water, toys can open the door for her to go out, but MUST ask her to sit first. Your behaviorist will help you incorporate other members of the family into her training. Your daughter needs to do some of the obedience practice, but ONLY if the dog is safe. If the dog doesn't show vast improvement withing 2-4weeks, I'd get rid of her. If there is any hint of aggression in other areas, I wouldn't mess with it, not with a young child around. If this food guarding is not completely cured, again, personally.....I wouldn't mess with this dog, unfortunately. Maybe you could find a trainer to take the dog.
Do get good professional help. This is just something to do in the meantime which may give her a jump start.
I am so sorry this has happened and that you're having to go through this stress. Keep us posted.
I hope Dr2little and Otch will see this thread and add some helpful tips. I always leave something out, even though my posts are so long.
PS. I just thought of something. If she happens to growl when you're hand feeding or anything, don't punish her with a scolding or anything. You want that warning to be in place. However, if she does, do not give her the food. Put it up and walk away for 15 minutes, read a book, clean something and come back and try again. Do not reinforce rotten behavior by giving her what she likes.
