I also hadn't found her, even though I tried out the lake exploration more times than seemed reasonable before that. But thanks to you asking and Tiny Dracula and ehroifcf's replies, I did find her and get her to move in.
Now I've lost Elyana again. I did her quest in the oasis and now she's not in her room anymore, she's not at the lake, she appears if I go fuck Orcs with Claire and after I do a breed vacation with Orcs, but isnt in her room after that either.