Sometimes a sudden dislike of something cannot be explained. Teddy didn't want to sleep in my bedroom for close to 6 months for no apparent reason. Now it's okay again.
I agree with taking her to the vet or a professional groomer. Trimming more often may help too, to regain familiarity with the process.
Patient re-training at home may pay off, but her nail growth may make time an issue.
I know Max will never let me trim his nails. Luckily, he files them down to the perfect length on our walks.