I'm sorry you and your baby are going through this. I know how horrible it is to watch them go through this.
If she does have a liver shunt, I'm not sure why your vet wouldn't be concerned about this. They can be treated. I believe there is a surgery that can help or I know they can at least be treated with meds and a special diet. One of the vets I work with has a Westie with a liver shunt that she only expected to live for a couple of years and she's going to be 9 years old soon and she has only treated her with Lactulose, Denamarin and a special diet that she makes herself (she wouldn't eat the dog food). I know you've already had 2 but I think I would get another opinion if I were you. If all of her bloodwork is okay, it may just be that she is epileptic. That won't show up on any bloodwork. I have a 6 year old Standard Poodle that is epileptic and he's been on medication for about 2 1/2 years and hasn't had any seizures since. The medication can cause liver damage so you really have to keep up with the bloodwork though. I have a CBC/CHEM done on him every 6 months and Phenobarb level once a year and there are other options for medication if they start to have issues. I hope you get it figured out.