“Based on my experience, I want to steer her away from the Duke’s of the spectrum and onto the honors colleges at State schools (including OOS) that would provide merit aid and bring the cost down from our EFC. I just can’t figure out if this is unfair to her.”
To me, “being fair” just means communicating how or what you are willing to contribute in an accurate and timely manner. It doesn’t mean sending her to the “best” school or maxing out what you could possibly pay for college.
It’s fair to tell her that if she is cost-conscious about undergrad, you will be in a position to help her with grad school, but that if she is full pay at a pricey college, she’ll be on her own after four years. It’s fair for parents to say, "We can contribute X dollars towards your four year education (or $X per year). If parents are unwilling to cosign any loans, say so before the kid starts applying anywhere, and likewise if you are willing to cosign, set a dollar limit up front. It is fair to say, "You can only go to Prestige U if you can get enough merit aid to make it work (and define “enough”). It is fair to tell your student that you will only fund four years (or whatever you can afford) and then they’re on their own - as long as you say that in a timely manner (i.e. before college starts).
It is not fair - and it happened the last two years on CC - for a parent (no matter how well-meaning) to say “Don’t worry about the cost,” and the kid gets in somewhere and the parents then say they can’t afford it. It’s not fair to refuse to give your kid any idea of college finances. If you can’t afford anything, say so when the kid is still a high school freshman and can choose to work to save up money and work hard on their academics in hopes of getting scholarships.