Frosty:
Some people have trouble because they dont know any tactics for Nessie type mobs. Some just rush in un-prepared. maybe you got extremely lucky and she didnt hit you with some of her more devestating spells. (earthquake comes to mind). Might be simply you went when you were higher than most take her on at in level.
For the Giants Sword there's several.
There's a couple that are random in chests but wont bother with those as thier are easier ones to get.
South East Wilderness Cathedral. 2 Death lords there that drop em. (one of the more promising battles if you go there at low teens IMO.
Mt. Wilderness. Barrow in the hill near the Dungeon Pillars. 1 Death Lord there. (also a chance from one of the chests in that same place if i recall correctly.
I know im missing atleast 1 or 2 more deathlords somewhere but oh well those 2 spots shouldnt be too hard specially considering your level your at (Mention of the Sane Mind spell kinda points towards what level ya are)
PS: basically "Every Death Lord mob drops a giants sword"