Tell her to check out neighborhoods in Hendersonville, Old Hickory and Mt Juliet which all border on Old Hickory Lake. Each is VERY convenient to Nashville though being on the north side of Davidson County she'll still be at least a half hour to an hour from you, depending on traffic. The Old Hickory lake was formed when the dam was put in on the Cumberland River many years ago and is huge. I have a lot of friends who live either right on it or within sight of it and they all love it. It is very popular for water sports, fishing, bird watching, etc.
The other big lake nearby is Percy Priest which is a bit farther south while still being close to Nashville but I don't know enough about the neighborhoods surrounding it to recommend one to anyone.
Welcome to Tennessee!!!