Nobody ever lost a gunfight because they had a few more rounds in the magazine.
I am not one who thinks magazine capacity is the most vital concern in a defensive handgun. I'd rather have shootability and a decent amount of power. Eight or nine rounds of .45 ACP in a 1911 works because I feel I can hit better with it than most higher capacity handguns. But if there was a handgun that could combine the balance, pointing, ergonomics, control placement, sights, and trigger of the 1911 with more capacity, while not giving up those fat 230 gr JHPs, I probably wouldn't say "no."
So I am with those who say there is no such thing as too much ammunition or too high a capacity, but don't think it is a substitute for other more important factors, like skill and "shootability." Make any sense?
If you are confident in your ability to place rounds under pressure with your six-shooter, then by all means, stick with it. But don't confuse yourself into thinking 17 rounds in a magazine is a bad thing, as long as she can do the same with hers...