It's very commnon to have problems with squirrels near bird feeders. It wouln't be so bad if this female came by a few times a day but she will parks her herself at the suet and continues all day to devore the food.
I found a tip on a squirrel site that said to put pepper flakes on the bird feed.
It claimed that mammals won't bother the bird feed with the pepper and has no affect on birds.
It seemed to work for the first few days, then the squirrel decided she would go for it.
(http://www.wrightwoodcalif.com/forumimg/nature/peppersquirrel2.JPG)
Sure looks like her tongue might be hot.
(http://www.wrightwoodcalif.com/forumimg/nature/peppersquirrel1.JPG)