Trimming nails is almost a 2 person job. One person to hold the cat, and another to do the trim. You can try a couple of things - first you can either wrap your cat in a towel which will prevent it from scratching. This works in a pinch, but they do have a product called a Cat Sac that you put the kitty in and pull each foot out through a slot in the bag. It basically immobilizes them with just their head outside the bag and the slot for the foot. This will keep you from getting scratched. You can order them at several places online - and some pet supply stores carry them. Sometimes a kitty muzzle that covers the eyes is helpful to keep them calm too. The last thing you can try is a product called Rescue Remedy. It can be purchased at any Healthfood store and is a natural calming additive you can give without worry. You can give 1/2 a dropper every hour to calm your cat.
If all else fails, let your vet do the trim. Mine charges $10 for a nail trim, and although I do most of my cats myself, I do have 2 that I have to take in as it is easier for me to do that than go through the hassle of doing it myself.
Good luck with your "pet-a-cure" ! Your kitty may not appreciate it when it's happening, but she surely will when you are finished!