Can anyone offer any advice on college ROTC for a High School senior?

I'm looking at her goals, specifically her chosen career fields. Civil Affairs is not an accessions branch, meaning she could not commission as a 2LT as CA. In order to go CA, she has to minimally be awarded a basic branch and eligible to attend Captain's Career Course.
If CA is her goal, I would recommend enlisting as CA, going in as an SMP Cadet - after all, maybe she gets a scholarship, maybe not; this way she will have GI Bill and Tuition Assistance to at least partially defray college costs while competing for a scholarship. This would have the added advantage of allowing her to gain some experience as CA before later coming over to the branch and most likely made a Team Leader.
Once she commissions, my advice would be to get at least PL/ Staff time, preferably XO or Company Command prior to re-branching to CA. That keeps her competitive for MAJ whether CA works out for her or not.
A degree in Public Relations would serve her well in several career fields, both civilian and military.
The key for her is to keep options open that help her attain her goals whether or not things less in her control (like scholarships) go the way she plans.

SGT Richard H., If you'd like to discuss this deeper, feel free to reach out directly to me. I actually work this exact job as a civilian in my CA unit in Minnesota.

SGT Hanner,
As a current ROTC Cadet I can say it is an incredible experience. If she is able to get a scholarship there is no better deal. However from what I've heard it is getting very difficult to get a scholarship so I would suggest completing all scholarship requirements ASAP and reaching out to PMS's and schools she is interested in. PMS's have a huge role in the scholarship department. If you/her have any questions for a current cadet please feel free to contact me.

First, I would find a school that she is interested in attending. Talk to the PMS and see what scholarships they have to offer. When I was enlisted, I called just about every school in the country that I was interested in. Texas Tech, Oregon, NC State, the list goes on. Some people will blow you off and some will help you out. That helped me figure out where I wanted to go for the next 3 years. Next, I would find a CA or Public Affairs unit closest to her. She could do SMP with that CA or Public Affairs Reserve unit while she is going through ROTC. I was an SMP Cadet with the 450th CA Bn (A). Civil Affairs is a career for officers who have already served PL and XO, and are usually looking at CPT. Another option available is that she can go to the National Guard. They pay a lot more for school than the reserves. They also have SMP, but no Civil Affairs. That may be a route to consider if she doesn't get a scholarship. Scholarships tend to be very competitive. I hope this helps.