I think Eliette looks pretty and sounds more feminine.
Thank you everyone. <3
Eliette is much better for girl.
NB: Elliott in Scrubs explained in an early episode that she was named Elliott as her parents had wanted a boy. I'm sure she said they were in denial, or something like that, so used a boy's name. Therefore, the show made it clear in that episode, that Elliott is a boy's name.
I prefer Elliot, but if you really only want one L, then Eliot.
Personally, I really dislike when people use the letter Y to make a name seem more "feminine". Just give your daughter a girl's name! In my opinion, Elliot is most definitely a boy's name. I love previous posters' suggestion of Eliette.
Eliette would be much prettier for a girl