maybe just by ein? wasnt she aware of how the duke really is? and i wouldnt really consider it as her being tricked. there's just no reason to show that side of him to her
imagine that u have a son or daughter just like ein and a husband just like the ml that teaches his kid things like that and then they appear normal to u, like just what ein and the husband did. wouldn't u feel kinda betrayed if u found out, especially when ur trying to make things better w/o really knowing what's happening for real around u. i feel like it's better for the duke and ein to straight up tell the fl what's really happening at their home, u never knoe the fl might understand them better with that.
Well, she ain't being tricked though, like the way Ein acts towards FL is genuine, he just isn't like that to other people. (⌒▽⌒)
for some reason i feel sad for the fl. like, she's being tricked by his husband and son, that's just too bad for me.