This might seem like a daft question, but wouldn't removing the existing selection and waiting to be auto-assigned something at check in actually run the potential for a much worse seat - ie. middle seat / last row - if everything else fills up before then?

At least (in my mind), having the seat already assigned is a step ahead guaranteeing she at least gets her preferred location (window).

If it were me, I would not gamble with the possibility that AA is "nice to me" and gives me a decent seat automatically at check-in without having a guaranteed back up plan already confirmed.