Maybe she thought Ein only became like that when he got older, that's probably why she thinks he's still innocent and that she can fix him before he goes mad ┑(￣Д ￣)┍ but idk even this doesn't seem convincing to me because ppl don't just wake up one day and decide to be evil.
Well in the original Ein was being abused by her so I guess she thought if she loved him and cared for him then he wouldn't become a villain
She new about her husband’s character to a point, but like @jen_jen032 said, she thought if she didn’t abuse Ein; he wouldn’t become evil. The possibility that Cassius was grooming Ein, didn’t cross her mind, because she thought it was “her” fault that Ein was bad. And Ein acting all innocent also played into her delusion. If he had acted true to his character, she probably would have tried to change his character, but she would have been more aware.
Also, she probably was prematurely patting herself on the back, thinking she had successfully changed both her husband and son’s characters… causing her to forget, at least Cassius’, original character.
Didn’t she read the novel about them before being isekaied? Then why is she acting like everything is new to her and she didn’t know about their characters?