Something in tartan would seem to me to be just the thing. You could always wait until the games and check the vendors for something she would like.
Also check the festival website before you go to see what clans will be in the clan village - Montgomery might be hard to come by but Shaw is pretty common. A visit to her clan tent should get her a good start on her heritage.
And congratulations on your upcoming anniversary.
President, Clan Buchanan Society International