Oh no! That’s really unfortunate. It does seem likely that he couldn’t see the weasels and he just remembered you and the chaos. I hope he’s able to settle down and trust you again!
I would try to gently clean around the injury (vetricyn is as safe as you’ll get) then apply a bandage to try to seal the area. Is a vet a possibility? Would she even survive a trip to the vet?
Oh that’s heartbreaking, FunnyFarm! I’m so sorry that you’ve had to go though this. :hitIt’s amazing that something as small as a weasel can take on something as big as a guinea! They sound like they were incredibly determined if they made you pry them off! I don’t know anything about successful...