Karen that is a new bowl and a new place, which is part of what makes the whole thing so weird. There were 0 issues over food until this weekend and the very first time I tried working with her on it, it ended up like this.
Have you been doing the exercise where she is on leash and you guide/release her to food bowl? She eats. You say out, guide her away from food bowl. Repeat.
Like shown in this video
[video=youtube;ZWyAA-7hedo]https://www.youtube.com/watch?v=ZWyAA-7hedo[/video]
If you have not done this, I suggest you start. Also, KEEP THE DOG ON A LEASH for control and safety reasons. See how you needed to grab the leash at the end because the dog didn't listen? Unless the dog is solid on kennel/crate command and will not attack you, you need a leash.
Also - I don't know why the dog went into resource guarding mode because 1. the dog wasn't even excited over the food (maybe that's just her) 2. dog didn't scarf the food down nor did she go after the kibble that dropped all over 3. she didn't break any of the wait commands. It looks like she redirected into resource guarding mode.
Some things I noticed:
1. At the start of the video - she's pretty relaxed. Once you've instructed her to mat - 1 lip lick and 2 yawns (signs of stress - might be out of excitement or maybe nerves)
2. Not once did she wag her tail over the food or while going to the food. When she was waiting for food and doing paw, etc. her body looks alert/attentive - seems normal
3. Once the food on plate exercise began - she became uncomfortable. Note position of tail - tense and close to body (sign of nervousness).
When she was done and came back to you and you told her to sit - she created space.
4. At 2:33, why did the lady say you won that one? The dog is confused. I don't think she understands the release word or does she? If she does, she might be telling you that she's uncomfortable going there.
5. Then comes the startle which comes the biting after 1 more plate exercise. It looked like she was going for the hand you startled her with?
It's hard to tell what the trigger is.
Some things to consider such as yelling and clapping when the dog is already in a heightened state of mind should be controlled. It usually escalates the situation. You want to be calm and redirect the dog. You gave multiple commands and none of them were followed through. Before you redirect them to a down or a kennel, you need to make damn sure the dog knows it and can perform it on a day to day basis no matter what the dog is doing (training sessions/proofing). I'm not sure maybe because the other lady was in the way so she couldn't go to her kennel or what, but it didn't look like she tried too hard to kennel (one look to lady and she sat).
and at 4:54 with the lunge growl - that's pretty scary - don't know how to make of it other than a challenge that she is being controlled or she has a negative association with such set up or maybe there's something not right in the head. I would have commanded her to a down (more submissive position) - if she doesn't comply, then just step on the leash.
I'm thinking this whole feeding thing is very stressful for her and she doesn't have a way of dealing with it and then it builds up and then she lashes out OR there's something not right in the head.
If I were you, I'd go back to basics and do a crap load of basic ground work exercises: kennel, sit, down, stay, come, place.