She may be experiencing allergies - it's common for pets to chew their
paws when they're having an allergic reaction. She may have something on
them also, something that's irritating them. Try washing off her paws
with some hypo-allergenic pet wipes or a very mild soap and water
solution and see what happens. If they're still irritating her, a vet
trip is probably in order, lucky kitty.. :)

K

Have you inspected her feet to see if a sliver or thorn is present?
Has she walked on small rocks?  Cats do clean their feet and between
their toes, but don't "eat" their  feet.  How do the pads look?  Are
they smooth or cracked looking?

If you mean she's sort of doing lick....lick....lick.....
nibble.nibble.nibble lick.... lick.... nibble.nibble that's normal.  
Sometimes there are little knots of fur to be sorted out or something
stuck that needs to receive intensive work.

Priscilla