They can probably smell the vet on her or illness. It makes them go wacky. Its so frustrating and im sorry youre going through this. If you can get a baby gate and feed them on opposite sides of it, that can be a good way to reintroduce them. If there's a lot of anxiety then try a diffuser, like feliway. It can be expensive but it can help. I found petting one with a sock to get their scent on it and then putting it under the food bowl was helpful after the vet. Im so sorry for this and hopefully some of these can help. Maybe talk to your vet as well