Не могли. О чем нам напрямую говорит LoTR
But Shelob was not as dragons are, no softer spot had she save only her eyes. Knobbed and pitted with corruption was her age-old hide, but ever thickened from within with layer on layer of evil growth. The blade scored it with a dreadful gash, but those hideous folds could not be pierced by any strength of men, not though Elf or Dwarf should forge the steel or the hand of Beren or of Turin wield it. She yielded to the stroke, and then heaved up the great bag of her belly high above Sam's head. Poison frothed and bubbled from the wound. Now splaying her legs she drove her huge bulk down on him again. Too soon. For Sam still stood upon his feet, and dropping his own sword, with both hands he held the elven-blade point upwards, fending off that ghastly roof; and so Shelob, with the driving force of her own cruel will, with strength greater than any warrior's hand, thrust herself upon a bitter spike. Deep, deep it pricked, as Sam was crushed slowly to the ground.
Таким образом, мы видим, что Шелоб было убить не так-то просто...
