You say she used to let you, was this when she was a pup?
Has anything else changed in what you can and cannot do with the dog? Think about training, recall, grooming etc.
When did it change? What age?
Any more info would be useful - if you have cut a too short and caused bleeding/pain at some point, don't feel too awful.....we all do it at some point/ points/every few months.....ummm, welll, you're not alone anyway!