Dogs in general seem to be "very protective of their feet". Maybe at a mellow time of the day when you give Sadie hugs and kisses, gently caress her feet and offer treats/praise. Do this off and on for days on end. As this continues get more agressive in her "foot massage and work your fingers inbetween her toes. After awhile Sadie might not be so "sensitive" or think twice about it.
Continuing her "foot massage" and then working your way into touching her nails, pulling gently on her feet, etc might make it not a big deal to her anymore.
Good luck and don't remember the hugs and praise. Not to mention a lady not liking a good foot massage.
