From the time you walk in the door as a new DB member you're told that Astrid has decided to ignore the following:

Tenet 1: Never dishonor the Night Mother.
Tenet 2: Never betray the Dark Brotherhood or its secrets.
Tenet 3: Never disobey or refuse to carry out an order from a Dark Brotherhood superior.
Tenet 4: Never steal the possessions of a Dark Brother or Dark Sister.
Tenet 5: Never kill a Dark Brother or Dark Sister.


However, it isn't until after Cicero's arrival that she violates Tenet #1. And not until way after that does she do #2, and #3.

So far as I know she never violates #3 or #4.

Since you can see the very worn plaques with the tenets in the Sanctuary, it's apparent the other DB members know the tenets and therefore know she hasn't broken them. So, why does everyone say she had decided to ignore them?

She had no superiors to disobey. Is it that you're not the first DB member she's betrayed or killed? Has she been wandering around bragging about what a great job she's doing in the nearest bar and telling everyone where they can find the evidence? Does she routinely steal Lizard Kibbles from Veezara? I suppose she could have been dishonoring the Night Mother regularly, but it doesn't seem to me that she would have had any time or energy or reason to do so.

So what's up with that one?

She tried to have Cicero killed (or did, if you're a faithful lap puppy), well after she started bad mouthing the night mother in front of him.

I don't think she ignored every tenant, number 4 especially... since we never see her actually steal from anyone, but she did end up betraying the whole sanctuary because of the PC's rapid development to becoming the night mothers new favorite toy.

Edit: As for number 3, the PC was basically the new listener and she wasn't about to start following orders by you, now was she?

What he said. She also tries to have YOU killed by setting you up for death at the hands of the Penitus Oculatus.

Also, we don't know what she said or did before we joined up.

Also, the general saying "Astrid ignores the tenets" doesn't have to mean she is purposefully breaking every single one of them right at that moment. If you violate my right to free speech as a US citiizen, it's fair to say you are ignoring the Bill of Rights even if you aren't simultaneiously violating all the other parts of it. If you commit advltery, it's fair to say you are ignoring the Ten Commandments even if you aren't breaking all ten of them at once.