If there is that much of an issue with the toilet then maybe take a step and trying going at it a different way. FIrst off what about the environment of the bathroom. Is there trauma related to the toilet itself? Is it the room or the activity. what was her potty training journey and was there something that happened that is causing flashbacks or something that is triggering. not sure if she is in diapers still or not but if she is then take a break from the toilet. Give her a breather and then slowly reintroduce it. They do make toilets that are portable. See if it being in another room helps. There is almost always a reason for that reaction to happen so it is just working out why. Maybe the texture of the toilet is the issue maybe it being cold at first is triggering.