"I know it is her decision, and I know how strong headed and independent she is"

Why do parents feel like they can't have all sorts of conditions attached to providing financial assistance to their adult children (yes, 18 is adult).

We basically had to establish the following understanding with our boys (mostly for boundaries for my wife):

1. Our love is absolutely unconditional.

2. Our emotional and moral support for your success and happiness is unconditional too.

3. We will provide financial support for the following:

• Health problems, disasters, and the like to the extent we are capable.
• Assistance with college tuition to BYU-I as long as you work full time in the summer and maintain a minimum 2.5 gpa
• Room and board while a young adult (within reason) as long as you are employed full time.

We limited college options to BYU-I because they weren't getting into BYU.  If they wanted to go to another school with similar financial costs, we referred them to item 2 and tried to help them find ways they could cover the costs themselves.  

We also told them if they were able to ultimately get accepted to a significantly better school, that we would do all we could to help pay for that as long as they lived a moral Mormon lifestyle.  Basically, we won't help pay for them to drink and have sex.

Why can't you tell your child that you won't fund something that you don't think will be in their best interests?  Of course you could be wrong, but if it is that important to you kid, you can help them work hard and raise the money for themselves and prove you wrong!