Complex sentence: Galadriel is sympathetic to Gandalf's explanation that he is afraid and the hobbit gives him hope, and thus offers her assistance, promising that if he should ever need her help, she will come.
Split into simpler sentences: Galadriel is sympathetic to Gandalf's explanation that he is afraid and the hobbit gives him hope. She offers her assistance, promising that if he should ever need her help, she will come.