Everyone else has given good advice and comments. Definitely keeping the bunny from getting to the incision is important- either with ecollar (most fool proof way usually), bite not collar, or belly band. Also the pain med issue should be addressed- if the bunny is in pain and trying to remove source of perceived pain? or the bunny is on pain meds so the trauma she is causing is not hurting much at the time of chewing out sutures and pulling staples.
Also- there should be some internal sutures also- which sounds like they were destroyed at first incident. But hopefully the second time the bunny only got a few skin staples out. If any further damage was done to the internal layers of the abdomen- it does need to be fixed! It could heal OK- but if it leaves a gap in the abdominal wall and creates a hernia that is very dangerous for the bunny- as the intestines can slip thru the body wall and then get strangulated, lose blood/oxygen supply and die. That would result in another emergency surgery for the bunny if you can catch it in time and bunnies are so, so sensitive about GI surgery- that is NOT a good outcome.
Another possibility to the cone, and physical ways of preventing the bunny from getting to the incision- is to use stainless steel wire externally on the skin layer for closing the skin- and leaving little tabs (excess) on the knots- it will create a poky barrier. Obviously THIS MUST BE DONE BY A VET- but I know that sometimes they do resort to this trick with small animals (hamsters, rats, etc to try to keep sutures in until it is healed). Stainless Steel surgical wire does not cause a suture reaction (the body does not reject it sometimes like other suture materials) and can easily be removed when incision is healed. (I had a cat that had an internal layer of wire sutures that showed on her x-rays- it was kinda cool actually).
But it does sound like a second opinion with another vet is needed- if some of the above things were out of the vets range of answers/possibilities- then they need another vet!!!!