With the caveat that I haven't worked with a dog this bad about nail trims, my first thought is to go back and start even smaller and slower. Which sucks to hear, I know. Counterconditioning/desensitizing can be a mind-numbingly frustrating, slow process. I'd consider starting with having the vet giving her as good a trim as possible under anesthesia so you have some time to work on things before she grows talons again. Another good stop-gap is a scratch board - I have one made of a cheap cutting board and skateboard grip tape but there's lots of tutorials out there for different styles - that you train the dog to dig at to help wear down the nails. It won't replace proper nail trims for most dogs, but in many cases it's a lot easier for dogs with nail trim issues to accept and be comfortable with because they're in control and it's more of a 'game' or trained trick in their eyes.
Set the (turned off) dremel or clippers on one end of a room, then walk over to her at the other end and have a treat party with super special, high-value treats for 5-10 seconds, no matter how she's acting about the tool. Then walk back over and put the tool away. Do this a few times a day until you start seeing a positive change in her reaction to the tool being set out. Then slowly start moving closer for the treat party (move back if you start seeing anxious or stressed reactions again). Eventually, once she's happy to have her treat parties next to the tool, you can start reaching towards it before you feed her the treat. Then you can touch it and treat. Then you can pick it up and immediately put it down and treat, etc. etc. You'll want to work on touching and handling her feet in a similar way (start with just reaching, getting closer, touching, gentle hold, firmer hold, etc.) WITHOUT the tool around - one thing at a time so you don't flood her.
For the dremel, when you've got her happy with you holding it around her and think it's time to get her used to it being on, you'll want to start over with being at a distance again, rather than jumping right to turning it on while you're holding it right next to her. Think of the sound as a completely separate category of thing to desensitize/counter condition. Hopefully it'll go faster as she figures out that you're not pressuring her and that nothing you've done so far has been scary. Only start combining all the parts when she's really happy and comfortable with each one, and always back up to the last step where she was comfortable if she starts stressing out.
One thing I try to do is have a different space for grooming/nail stuff that is mandatory and for where we're doing this kind of cooperative care work. That way, even if I have to take care of something before we've fully worked up to it (and I have curly dogs so I can only avoid uncomfortable/stressful grooming so much), the cooperative care scenarios still look different enough that I'm not completely poisoning all the work I've done.
But I do suggest you check out the cooperative care facebook group if you want more information and support (Facebook Groups
). They have a ton of people who have way more experience working with really difficult cases than I do, and will be way better at troubleshooting and knowing ways to help make it work for you and your pup. The creator of the group, Deb Jones, also wrote a book on the subject (Cooperative Care: Seven Steps to Stress-Free Husbandry) and has a class specifically about dealing with nails coming up in December on Fenzi (Fenzi Dog Sports Academy - FF190: All About Nails
), if you want more guidance than the group can provide.