Army AROTC and NROTC- MO Marines are less particular about choice of major when evaluating candidates - at the front end and as compared to scholarship selection in the AFROTC which isn't subtle about their preferences and NROTC-NO Navy option who have calc-physics requirements that they need to see you have a potential to pass. NROTC_Nurse Option is of course partial to those intending to pursue a nursing degree. But overall, go for it in applying and know that people without tech majors too do get scholarships - just with AFROTC, overall less are given outside of tech- but some ARE given out of tech too.
I would just accept that for Army she that major will not count against her in the scholarship selection process. I do not have line of sight for what that major will impact for her branching choices when commissioning and moving forward with her career, but as others said, the OML drives freedom and choices - stay out of trouble, get great grades, advance in leadership within your unit, be active, curious etc., excel in your PT, volunteer / don't do the minimum etc to give yourself your best shot. And, don't get lulled into the BS a lot of people put up on how their major at their school it's OK to get a 2.7 GPA because it's hard - don't plan to have lower grades - plan to excel.
Good luck.