Increasing watch size is a trend. Watches have not always been comically large.
See:
http://www.ablogtowatch.com/whats-deal-big-watch-sizes-large...
http://www.nytimes.com/2014/11/21/fashion/trends/watchmakers...
See:
http://www.ablogtowatch.com/whats-deal-big-watch-sizes-large...
http://www.nytimes.com/2014/11/21/fashion/trends/watchmakers...
40mm is actually on the smaller side for watches. Divers start at 42mm typically. The Apple watch she purchased is also 42mm.