it's weird, but I heard that a lot of the story of Lord of the Rings relates somewhat to the Bible. Supposedly Tolkien wanted to re-write the ideas of the Bible in a non-religious way.

Perhaps her giving up her eternal life was supposed to be similar to Jesus? That is, of course, except for the most important factors like the actual value of Jesus' life and reason/need for his sacrifice. False Religion is stupid. It always misses the point.