@HRoFan - anything is possible. Once I say that something would be difficult, someone will respond with a story that it was easy for them!! So, yes anything is possible. A BA to a MM in VP is certainly do-able. But here is some food for thought.
I’m not sure that the concern for the MM should be on the academic side bc as always the audition is king. I would not be so concerned about what is missed on the academic side (with the exception of language/diction study). I’m sure that she would be able to get a good basis in theory in a BA and hopefully languages. And she can do some remedial work in grad school if necessary.
I would be more concerned about being up to snuff on the performance side. So I would highly suggest going to summer programs to stand next to kids at BM programs to be sure that you are advancing as necessary (note that good programs do require an audition). My D did get placed in opera chorus Freshman year, mainly I think because she is so naturally loud…and mezzos are usually in demand. She always stuck out in high school choir even as an alto/mezzo. The first time she sang with a lot of grad students, she was stunned. She could not hear herself since everyone’s voice was so large. She was very disconcerted…and told me she had no idea what she sounded like. Also the school’s auditorium pulled your voice out to the audience so even in auditions (done each semester) it was really difficult to hear yourself. In other words, you better know your notes and have good muscle memory. This would even trip up some new grad students on occasion. Freshmen were told to wait on auditions due in part to this. My D did audition second semester Freshman year as she was getting used to the stage and growing her voice…she had no choice as her peers were showing her what could be done.
More than a concern about academics, I have heard (from my D) that schools do look at where/what you have “performed”, meaning school, roles and summer programs to get an idea of your performance ability. My D did note that from selective BM programs, most students worked at a similar pace (fast) to a similar quality. She did do a summer program in Europe that had more a mix of students and did notice that the pace was slower and the expectations lower. The end product was fine…but the process was definitely different from her school…and not bad when you are in Tuscany! But at other selective summer programs, she found the pace and quality high.
For grad school, they are looking for “performers” at the selective schools. My D got a good deal at her school (less selective explained below) bc they needed a performance-ready mezzo for the upcoming year. So I would be more concerned with the performance side of the equation.
And…one other thought…it is really difficult Senior year of high school to know how a vocalist will grow. No matter how hard you work as a vocalist…you don’t have full control over the development of your voice. Soprano grow faster. Mezzos take longer. If your D is locked and loaded on opera, it may be best to follow the beaten path…meaning a BM at a selective school.
However if your D is undecided about opera, there is a lot you can do vocally that is not opera. In that case, you don’t need to necessarily worry about the selective programs. My D got off the beaten path for grad school, choosing a less selective grad school (which covered tuition) despite getting into some selective programs (that at best covered 50% - still good but no guaranteed to perform…my D wanted roles and was promised them at the other school…she did not want to take the chance to pay big bucks and get one supporting role…right or wrong it was her choice). She felt that she could be happy doing other work besides opera and wasn’t sure she wanted to put the work into her voice for years for the slim chance of making it…her opinion after watching some “giants” in opera get most of the opportunities. She questioned if she would really get there…and was OK with maybe not. Now she continues to do some regional opera but also does a lot of other interesting works vocal work as well as theatre, MT, commercials. So it’s not always an “all of nothing” proposition to perform vocally. But to “make it big” in opera…you do need to “hit” certain basic performing opportunities at certain schools/festivals in UG or be very, very “special” vocally. At least that’s my opinion.