Whether it's clipping my horses (2 and use to have 9) ears or cutting my dogs (5) toenails the one thing I have learned is not to make a big deal out of it. The main thing is that nobody gets hurt and it is not an unpleasant experience. If either of the two happens I assure you every time you try it will be a big ordeal that nobody wants to be apart of.
Start off slow by doing nothing more than lightly rubbing her feet and toes a little. This will accomplish two things. One it will show your dog that every time you go for her feet it is not to cut her nails and an unpleasant experience and two if she does have arthritis or some sort of inflammation in her feet or legs which is bothering her.
After about a week or so graduate to having the nail clippers so she can see them when your gently petting her feet. Do not clip her nails the first or second time. Then clip one taking just a little off and making sure your clippers are sharp enough so that it doesn't pull or tear. If you cut to far and hit blood I assure you it will ruin everything. Do one or two at a time a day or every other day until they are done.
I do this with horses whether it's a bridle path and ears being clipped which I now do without a halter or them being tied and with my dogs. My dogs I can do while I'm watching tv, after they get a bath or whenever because it's never been a big deal and I started slow. They also know I would never hurt them.