Smith has a resource for just this sort of question:
https://www.smith.edu/about-smith/equity-inclusion/gender-identity-expression
They make it very clear they are generally inclusive of nonbinary students, although they do also say people who identify as women, including nonbinary women, are eligible to apply.
There is also a Trans/Nonbinary Working Group, with its own email. I am sure you could contact them with any specific questions you might have about what that means to them, or any other questions on this subject you might have.