Are you being unfair? YES.
You are being unfair because you are interjecting your opinion into her deal.
You are being unfair because you are suggesting that she give up her tuition because she is married.
You are being unfair in trying to equate being married with some kind of supposed special responsibility which removes your parents from her life. I'm wondering where you got the idea that once married parents leave your life. This is not some principle, it is a silly proposition. Don't you think most parents would happily pay for school and the downpayment on their kids house if they had the means?
You are being unfair because you appear to be exercising some sibling rivalry maneuver which would remove her tuition
and probably cause her to leave school.
IN MY OPINION, based on no other information than here,
you sound like a spoiled sister who is trying to get in the way of her sister's happiness and career. Whether this is jealousy or some convoluted view of marriage as total independence I cannot tell.
What is your motivation for pressing this attitude?