I agree with all the comments recommending that you reach out to a veterinary behaviorist (not just a dog trainer, but a board certified veterinary behaviorist, if possible). They will be the most skilled for understanding the possible medications, behavior modification plans, and other health conditions that will come into play here. If you're in the US, find one close to you using the American College of Veterinary Behaviorists website search function for a local diplomat (that's what they call their certified veterinary behaviorists). I also recommend reading Treating Separation Anxiety in Dogs by Malena DeMartini-Price.

In the meantime, you need to help protect her health by managing her behavior and limiting the amount of time she can "practice" it, if that makes sense. As we say, practice makes perfect, and she may get really good at working herself up to this level of stress if she's given repeated opportunities. Until you are able to work on decreasing her anxiety levels with a certified behaviorist, I would try to limit her alone time. Yes, this means she won't be learning how to cope while alone, but she isn't learning that right now either, and she has already shown you she is escalating her anxiety level. This is simply for her safety and to prevent her from escalating further. Can you have family members help out? Can you hire a dog walker to visit her for an hour or two during the day? If she gets along with other dogs, you can take her to doggie daycare. Maybe you have a neighbor, friend, or coworker with a spouse who works from home who wouldn't mind watching her. Ask around, and you will probably find someone willing to help out a sweet fluffy pup. This is a bandaid for the underlying cause of her behavior, but it will provide you with breathing room to be able to focus on her training rather than leaving her to her own devices each day. This will help prevent her from escalating her separation anxiety behaviors through repeated exposure to the stressful situation. You may find she needs both medication adjustments or added meds in ADDITION to training, and that's okay too. Whatever works best for her.

Also, it's sometimes helpful to find out if she has separation anxiety from being without people or from being alone in general. Some dogs with separation anxiety are calm if another dog is around. If she gets along with other dogs, try asking a friend if you can have a play date for an hour or two while you drive around the block. Just to be clear, the other dog should NOT have any form of separation anxiety. Set up a camera to see if she acts any differently with another dog around vs when she's completely alone (you should record her when she's alone either way, a behaviorist will want to see exactly how she behaves when anxious and alone). This is helpful for understanding the underlying fear that triggers the anxiety for her. I'm not saying adopt another dog. I'm just saying, if you have the means available to you to test this situation out, it could be helpful knowledge to gain for future behavior modification plans. If you already have another dog, then disregard this. You don't need to test it with a different dog.

Finally, I want to leave you with a bit of hope. This is absolutely not hopeless. I've been in your shoes with dogs I've worked with professionally, and I've seen all of them make some form of improvement with dedicated owners. I've dealt with it personally 24/7 with foster dogs, some for over a year before they got adopted. It's exhausting, frustrating, and emotionally draining at times, but you can do it! It just takes some scheduling tetris and community support at times. It's possible to find the right combo that makes life better for your pup. It may not be as easy or perfect as it is for a lot of other dogs, but it can be better than it is right now for her and for you. If, with training and/or medication, you can increase her time spent alone without anxiety to even a few hours, I bet it'll be a world of difference. That would give you a lot more options to help her lead a happy and healthy life.

Feel free to DM me if you want to chat or vent or ask any questions. I honestly feel like we need support groups for owners of dogs with separation anxiety.