If you marry inside or outside of your family does not matter (normally).
The wife will be the female holder of the male's titles when they get married and therefore use his CoA.
If the male dies before the female, what happens depends entirely on the rules of that court as you all know but the base CoA stays with the holder of the title.
If she does not get to keep the title, she will be given a different title with a new CoA for that fief.
If she is not goven a new title, she becomes irrelevant and does not need a CoA.
The purpose of male offspring is to secure the title, which is why using cadency devices makes very much sense.
They are saying "Look, it's the Duke of Exampleland! Oh, soon anyway...".
Female offspring, I don't even know if they used to use CoAs since their purpose was to get married.
If they did, they would follow the path described in the first paragraph.
If you don't consider a title important enough to display it on your CoA then that would be your decision.
That would however make your claim less secure with time I suppose.
This can be seen in the official list of titles for nobles with cluttered CoAs versus the ones who only kept the big one in my opinion.
Also, if you claim a title you are not in posession of, that would be symbolised by you suddenly displaying the heralidics of your previous superior or your rival impaled with your previous one in a lot of cases.
Or for added effect, claim that you belong to an older dynasty that were holders of the title before the current one and display their CoA.
That could have some drastic effects on their legitimacy and thus morale.
The wife will be the female holder of the male's titles when they get married and therefore use his CoA.
If the male dies before the female, what happens depends entirely on the rules of that court as you all know but the base CoA stays with the holder of the title.
If she does not get to keep the title, she will be given a different title with a new CoA for that fief.
If she is not goven a new title, she becomes irrelevant and does not need a CoA.
The purpose of male offspring is to secure the title, which is why using cadency devices makes very much sense.
They are saying "Look, it's the Duke of Exampleland! Oh, soon anyway...".
Female offspring, I don't even know if they used to use CoAs since their purpose was to get married.
If they did, they would follow the path described in the first paragraph.
If you don't consider a title important enough to display it on your CoA then that would be your decision.
That would however make your claim less secure with time I suppose.
This can be seen in the official list of titles for nobles with cluttered CoAs versus the ones who only kept the big one in my opinion.
Also, if you claim a title you are not in posession of, that would be symbolised by you suddenly displaying the heralidics of your previous superior or your rival impaled with your previous one in a lot of cases.
Or for added effect, claim that you belong to an older dynasty that were holders of the title before the current one and display their CoA.
That could have some drastic effects on their legitimacy and thus morale.