When you get these very long letters early in the correspondence . . . they are usually 'canned' letters.
Nothing wrong with canned letters early in the game . . . if they are really written by the gal in question, and if they actually help you learn something true about the gal, her thoughts, emotions, etc.
Just don't get too smitten thinking that she wrote all of this just for you.
Love is a word that should never be written or spoken this early in the relationship. It should not be spoken or written until after a lengthy first set of meetings on a first trip, and probably not until after 2 or 3 more trips with a lot of time spent together.
I did have one gal say it to me on second day we were together, but it didn't send a red flag to me because I felt she really meant it and I didn't think she said this often. We had had a lengthy pre-meeting correspondence and she really liked everything I had written.
We spent a lot of time together on 3 trips. As time went on, our relationship became more stormy, primarily because she was an 'in your face' type of gal who never left anything unsaid.
We still correspond infrequently, and a few times she has said she still loves me very much. I believe her. She has had 3-4 other boyfriends in the interim.