Galadriel spent 1000 years in the light of the Two Trees before going to Middle Earth, being active during that entire epoch, then went back to Valinor. She's upwards of 8,000 years old by The Return of the King
Which makes the idea that our heroine is a 'young, impetuous' Galadriel laughable. She's at minimum 2,000 years old when she fights that ice troll.