Some current nomination info can be found here
Service Academy Admissions - Welcome but the above comments are on target. There are MANY candidates who seek multiple nominations with no real conflict. She should especially consider USMMA as an alternate (if any Academy can be an Alternate) as you can continue in the Coast Guard after Graduation. It is a credit to her integrity that she is remotely troubled by her consideration of the impact on multiple Nominations. Good Luck!