“Her body type is minority” is a bit of a strange thing to say, like “minority” is a body type. From your explanation, you meant to say “Her body type is in the minority”, so I guess it was a misunderstanding.

Is the word minority so attached to race that it’s not used to talk about relative sizes in groups (if you understand what I mean)?

In that case I will not use it like that in the future, thank you for explaining!