Specifically, does it look unprofessional when a woman has hair that goes down to her waist (or beyond)?

My hair currently goes down to my waist, though it has been longer in the past, and I don't intend to cut it any time soon. The problem is, I have an interview at a medical school coming up on Tuesday,* and I'm concerned that my long hair might not look professional.

While I'm sure that the standards for what is or isn't professional vary among fields, with the creative ones being more lenient, it seems as though hair that approaches the back bra strap is considered too long to be professional. (I am surprised that people even consider shoulder-length hair to be long.) This is so annoying to me, because I believe that hair is a form of self expression. I'm already not allowed to put pink highlights in my hair, so the least I can do to have it naturally look striking is to grow it out longer than most people's.

I have only recalled seeing one female physician with long hair, that was let down, being interviewed on TV. One question that comes to mind is whether the people who enter the profession already chose to have shorter hairstyles prior to entering or if they felt the need to keep their hair under a certain length because of the requirement to look professional. Perhaps it isn't an issue for most of them because nearly all the people I know have shorter hair.

My opinion is that judging someone by their hair is superficial. It is my answers to the questions that should matter more. However, since it still happens, I will need to figure out how to get around this problem without cutting my hair. I don't play with my hair while I talk, but I think I will still tie it in a low ponytail. I would prefer to put it up in a bun because that way the actual length is not obvious, but I'm not sure how to make a neat looking bun and have it stay securely for up to six hours. (My hair is too long to put up in a French twist.) I've also read that a woman's hairstyle shouldn't be too elaborate, because it will give the impression that she spends more time on her hair than her work, which I think is an unfortunate judgment. Any other suggestions for professional hairstyles for long hair?

*Some of you may not know that I don't actually want to enter the medical profession but my family is pressuring me into it. Anyway, I won't write about that here.