She accepts the letter without looking closely at any external details.
If these seem arbitrary and disconnected, they do to me too.
Lying you know about. You can also gain karma from keeping promises or succeeding at tasks you've announced you'll attempt. This is almost never worth trying; it only works if there's a good chance of failing.
Attacking an enemy without warning is frowned upon, but if you believe you're fairly retaliating for something they did, that's encouraged. This has the obvious effect with promoting feuds. You can get karma from acting an assigned role. That works even if it's self-assigned. Think of it as an implicit promise. It is possible to inherit karma, usually but not necessarily going to the oldest child when someone dies. Oldest child regardless of gender; magic is very gender-neutral nearly all of the time. Discriminating between them would be seen as weird, and they spirits prefer statuses quo.
It is very important, especially if Men ever turn up and start becoming practitioners, that you not just think of individuals as interchangeable "latest scion of the house of whatever." That happened on my world, and now the basic unit of practitioner society is the bloodline or equivalent.
If you have a visitor, you offer food and drink because if you don't they might starve before they reach the next house. Almost never true, by the way, but it was when the rule caught on—and if you're a guest you don't abuse that or you might be killing the next person. That offer is also a truce of sorts. Even if the visitor is an enemy who you'd stab in the back and have the spirits side with you, you don't betray hospitality.
People are responsible for their own actions, Spirits are usually not very willing to accept coercion as a defense, but in extreme enough cases it's someone else's action done by your hand. Most possible actions don't have specific rules about that situation in particular—doing something is good is if it helps or harms people by those people's own lights. Not very clearly defined, but it probably can't be. It's worth having all practitioners run that in the back of their mind all the time.
People matter, and everything else in the universe is useful scenery.