It is some times hard for them to learn to like having their nails done, but it is necessary. If a nail left unclipped for too long curves under (as they naturally do) it can grow back into the foot pad. VERY BAD !!! I have seen it (as a pet groomer)

Some hints:
Do one nail at a time if that is what it takes.
Be confident and hold them firmly.
Let them be in THEIR most comfortable position (this will be the position where they squirm the least)
Get help. 4 hands are better than 2
Find a mobile groomer that is willing to come to the house, or if you are on good terms with the staff at your vet maybe one of the techs might be willing to hmake a house call (they will all know how to handle her)

Hope this helps at least a little.