Congratulations on your D's success, Shrinkrap!
I guess if an ineligible student REALLY wanted to spend the $60 per campus (knowing they would not be considered for admission) they could get around the online application lockout by printing the paper application and mailing it in.
The summer before senior year, nearly all California high schools submit the transcripts of their top 10% of students to the UC for evaluation. (Juniors get a letter in the spring requesting permission to submit the transcripts - if they don't give permission, their transcript will not be submitted.) You can check to see how many transcripts your D's high school submitted by searching here:
https://www.ucelc.org/ucschoolstatus...tus_search.htm - you don't need the "ATP" code, just name of school and city.)
The UC evaluates each transcript and then sends letters telling the students they are either 1. ELC (Eligible in the Local context - VERY helpful at the selective UCs), 2. On Track to Statewide Eligibilty, or 3. Not on track to Statewide Eligibility (meaning there is no way they can - in the one year of high school left - get all the courses needed to become eligible.) Eligible students are directed to the online application that has already been set up for them. There are eligible students (that other 2.5%) who do not get the letter - and they can start applications on their own - but hopefully they will do the calculations to determine if their application will even be considered that BEFORE spending the $60. By its own rules, the UCs are only allowed to consider a tiny % of ineligible students (and as a public institution they are often audited), so they are very strict on that point.
Like your D, I was very pleased (and relieved!) to be accepted at my UC choices, and like your D, I also chose another option. It was a very difficult decision because (it is probably obvious) I am a big fan of the UC system.