Jenette was artificially born out of black magic. Just by being close to Athy and Claude, the black magic around her could inflict threat to them, without her knowing ofc. Claude was already using some sort of magic on himself before (I forgot if it is some sort of black magic but it causes him to get rid of his memories of Diana). The ribbon Jenette gave to Athy clearly has black magic, and the bro (Well, it is Aethernitas but) timed it perfectly when Lucas was out of the picture. He knew Claude would save Athy and caused him to slowly die. Since Jenette was born out of bro’s black magic, she could temporarily get rid of Claude’s illness (unconsciously ofc) just by being by his side, but it’s also strengthening the illness. So yea, basically, Jenette is a white lotus being used by her father (or well) without knowing anything. She doesn’t really have any sort of crime. Except her existence itself is a threat to Athy and Claude. ╮(￣▽￣)╭
I almost want to delete my comment and replace it with yours
I'm bad with words
But this is kind of what I wanted to say too
I don't think Jeanette is causing Claude's death
I think the brother is using her
He made Claude ill obviously and also made it so that Jeanette could alleviate his pain or whatever so she could gain his trust
Maybe his love too, he probably does not even realize he is dying
Imagine you are in pain and can't even sleep you would obviously feel very greatful to whatever is helping you rest and maybe the plan was making Jeanette his heir