
Your husband raped his brother (Seth's also your brother) in front of you. Admitted that he stole Seth's seed so he can't bear a child with Nephtys and to top it all off, impregnated Nephtys and scammed Seth to believe that Anubis is his flesh and blood. Stop covering up for your psycho husband like an embicile and let Seth take his revenge.

Well, if Seth dies (with his soul vanishing):
1. The gods will not find out about what her husband did to Seth and Horus will probably be the one who inherits the throne even tho his father Osiris did something unforgivable (that's what she was aiming for from the start)
2. Seth's soul will be crushed so he will not be able to be with Osiris in the underworld.
Isis knows that her husband doesn't love her and if Seth dies without his soul being crushed, he'll be with Osiris in the underworld forever.

She even wanted to confess what happened but then she saw Seth's reaction and chose not to reveal the truth. She still wants to destroy Seth for both the wrongdoings he did to her (he wanted to bed and marry her after killing Osiris, then she had to crawl in darkness in labyrinth and then Seth destroyed Isis's temples and slaughtered women resembling her so she had to hide in poverty and slams while being pregnant and Seth didn't even know that Isis knows the truth) and mostly to hurt Osiris the culprit of the whole mess but decided to at least not "humiliate" Seth like that (basing judgment on his reaction).
Is like a jealous wife. Lol. They are so cute in this chapter ( TДT)