Mehul,
My thoughts are to do the rifle as I said and use the existing stock as the trainer and she can grow with it. My thought and this applies to me and not neccisarily yourself is that I don't know when my time will come hopefully not for many years as I am not that old (55) but I wanted my daughter to have something that would always remind her of me and our times together The 69 works into a nice adult sized gun and it is something I know my daughter will always cherish.
Whatever you decide the thinking about it and the planing are almost as much fun as the doing.
Good luck in your endeavor.

Michael J