Well, I have learned that a few hours won't be too bad, but 7 hours and up I believe counts as missing one pill.
It's not too bad to miss a pill, you just keep taking them regularly. Missing one pill is ok and you can keep on without having to use backup but missing 2 or more, you have to use backup for 7 days to get back on track( some pills can take 14 days, it should say in the instruction paper that comes with the pill).
So, she took hers at 8pm instead of am, no biggy just take tomorrows pill at the am time and keep taking them regularly from then on.
I'm always a few minutes off, so is probably a lot of the female bc population. Minutes happen.
But a lot of hours, that can hurt efficiency.
Hope that helped.
Liveinlove