Yes, you have to keep trying. If you let her win then she will learn that all she has to do is whine and jerk and you will leave her alone. Just make sure you are not cutting them to short. Some people recommend giving them a treat when they allow you to touch the feet. I have never tried that. The best thing is to invest in a grooming table with a grooming arm on it. A small table like the one shown in the link below might work well enough for your needs if you don't want to invest in a full size grooming table.
PetEdge: Master Equipment Small Pet Grooming Table - Pink Top