It is traumatizing for many birds to go to the vet. However, seizures are a serious enough situation you NEED to find out whats going on. It won't work for her next visit, seeing as it needs to be done ASAP, but you can start working with her at home to train her to accept being toweled. That will take months probably to slowly introduce her and get her used to it, but in the long term, it's a worthwhile venture. You can then bring the "safe" towel to the vet (which she is used to) and of course, her favorite treats to reward her afterwards. And of course, you should also work on socialization too. But that all takes time. In the short term, however, she will just have to deal with the stress. One immediate thing you may be able to do I can think of- Our old vet (not avian, but was the only one within a 2 hour drive who would see birds) used to let you sit in the exam room for a while before the vet/vet tech came in. I'm not sure if it was he was busy or intentional, but it gave you the chance to calm your bird down a bit rather than going straight from the stressful waiting room full of unfamiliar people/animals to being manhandled by strangers. He also let you have a few minutes to calm your bird down after the exam/tests before you packed them up to go home. It made it at least less stressful and gave the bird a break between stressors. Perhaps your vet would let you try this when you take her in for her blood test?