We had this same dilemma with both DD and DS. My kids simply ended up listing the schools in order of what they truly wanted. DD ended up listing 5 schools for both Army ROTC and Navy ROTC Scholarship. For NROTC, she was offered the scholarship to her #1 choice (which was the most selective one on the list) in the fall before admissions decisions came out. We were sweating out the admission decision, but were blessed when she was offered early admission to the school in December. When we went to visit the school in January and spoke with the NROTC unit, they had advised us at that point 17 kids had already been awarded scholarships to that school, but only 8 had been admitted at that point. He told us that every year, they do have students who don't get into their school and have to scramble to try to get their scholarships transferred to another college. The problem, though, is that by the time they find out they don't get in, many of their 2nd, 3rd or 4th choice schools have already met their quota for scholarship winners, especially if they are a rolling admission school. So the offer for the scholarship may be pushed down to the last choice school. When we toured another very selective school, that detachment told us that they can never fill their quota of scholarships as they typically have so many scholarship winners who simply don't get admitted into their university. He suggested that even if their school was the applicants #1 school, to move it down to the #2 spot on the list and move up another college into the #1 slot that they believe they would definitely get into (and be happy attending if they aren't admitted to their top college). Then later, if they do get admitted to their true #1 school, ask for the scholarship to be transferred to it. This only works, though, if the #1 school never fills their scholarship quotas.
Recently, for Army ROTC Scholarships, all of the 1st board scholarship winners were awarded scholarships to their top 3 choices to decide which college they wanted to attend. On the downside, they had to make their final college decision, before the selective schools had made their admissions decisions. The year my DD got her 4-year scholarship, she did not get it until the 3rd board. By that time, her #2 school had already reached their scholarship quota (she called the ROO at the school to confirm), so she was awarded the 4-year option to her #1, #3 and #4 choices on her list. By the time she was awarded the scholarship, she had already been admitted to all 5 schools that she had listed on her application, so she didn’t have that to worry about.
I would talk with the unit/detachment of your child's #1 school and get advice from them. Find out if they meet their scholarship quota each year and if so, how quickly they do so. Find out how many scholarship winners typically accept the scholarship, initially, but then later decline them if they get into a Service Academy or choose another branch's scholarship. In that case, if you remain on their "waitlist" then you might be able to transfer the scholarship when that happens. I would also say, that if your DD is not selected in the first round of scholarships, keep checking in with your her top schools, to see if they have given out there allotments already. If that is the case, she may wish to select new schools for the list or reorder the priority list of schools.
Many people on this site will tell you to have your DD choose a college that you could afford for her to attend, even without the ROTC scholarship. There can be many reasons why a cadet/midshipman does not make it through to commissioning (over 50% attrition in some programs), to include not passing PT test, being overweight, not passing classes, alcohol/drug related issues, medical issue that comes up, sports injuries, car accident, deciding it just not for them, etc. If she loses the ROTC scholarship, can she afford to stay at that school? We took a different stance on this. There are some great private schools out there that are not affordable to most families (mine included) without these scholarships. But we saw this as an opportunity for her go to her dream school. I do think, you must go into this process with your eyes wide open. Yes, there are horror stories about students being kicked out, or quitting ROTC and owing $180,000 payback. This has happened. What if she develops an illness or a permanent injury that disqualifies her from continuing in the program? She won’t have to pay back the ROTC scholarship in that instance, but can she afford to stay at the college? Ensure you all know what the scholarship contracts says before she signs it and what the ramifications are if she don't make it through. If that were to occur, what would she do? Would she transfer to another, more affordable college? Even if the fall-back college had initially offered your DD a scholarship with original their admission decision, will they still offer scholarships if she were coming in as a transfer student?
Good luck to you and your DD through this whole process.