How I see it, Eveline is a virus. A self aware virus I guess, If youre infected, she can make you see shit, like see a little girl teleporting all over the place. Her physical form is the old woman, which looking back, makes it extra creepy because she was there at the start and stalking you throughout the game.
And dont forget, Eveline WAS a little girl. She eventually grows old (rapidly) with the Bakers. And the Bakers dont need to see her as anything, for them shes part of the family, like Mia is. Because the virus makes them think they are, the virus is obcessed with family.
this
for example, after killing marguerite, the whole "ring like" sequence, where the walls have kid drawings and then seconds later when you see the little girl legs and come out, the walls all have fucked drawings. That wasnt old ass eveline quickly drawing on the walls lol, that was ethan seeing what she wanted him to see. One can assume that the mind control comes much later in the infection process, so she could only mess with him a little but not fully make him part of the family.
