And if you can cut them after her bath, they are really soft, a lot easier to cut. Don't worry, you are not the only one who has done that. When Sarah was about two months, I did the same thing, except I cut off too much and drew blood. I cried longer than she did and felt like a terrible mother. But stuff happens, she'll heal and won't even remember what happened and you'll still be the same wonderful mommy to her.
Also, I had Rob distract her with her head turned away and while he was entertaining her, I cut her nails, she never knew I was cutting them since her head was turned the other way watching Rob.