I can give some vague answers on how things worked for my daughter (University of Portland / Class of 2014). If you didn't know, pretty much everybody in ROTC will complete a 4 year class "schedule" (there's an official form name which I forget) you will to make sure they are taking the right classes to graduate in (4) years. Engineers and maybe others get (5) years. The school also had certain "core" classes that all nurses must attend in the 1st (2) years and have a certain GPA in those classes to move on to upper division course.
My daughter had a fellow nurse roommate (my son, not a nurse, has all AROTC roommates). There was a brief moment where there was some concern about getting ready at 0530 (3) days a week and bothering the roommate which turned out to be a non-issue. If it were me and you had a choice, I'd go with an ROTC roommate so they're both getting ready at the same time.
Between the required nursing curriculum and what the Army requires nowadays, she'll most likely be busy EVERY Summer break. The Portland nurses go to CIET after their Freshman year (they didn't have this when my daughter went thru), whatever LDAC is called after their Sophomore year (normally a junior year thing but the school requires they do a nurses rotation that year) and then the Army also has a medical rotation they do their Junior summer as well where they could go anywhere in the US. My daughter went to Texas but some of her classmates went to Hawaii, Colorado and DC for the month.
The best advice I can give is work hard THIS summer and show up ready to kick some butt on the 1st APFT testing cycle. Study, study, study because those nursing classes aren't easy and make sure she knows what she has to do to move on to upper division. The majority of Nursing schools are competitive and they have some crazy points systems that give preferential points for a variety of reasons...and being in ROTC means pretty much zilch.