I wouldn't overthink it too much and wear mostly what you're comfortable in - it isn't a beauty contest, it is an interview for vet school although I do think they don't mind seeing some personality (e.g. I like to wear a bit of colour). But do look over the vet school's interview process as some may ask you to animal handling etc so may impact what you wear, particularly footwear. I think smart casual is the ideal vibe but I do think they won't judge you for being too smart but too casual is possible - i.e. possibly joggers + hoodie may not be the most suitable thing, I also wouldn't wear massive heels or something that might make animal handling awkward. I think all trousers (like chinos), reasonable length skirts (I wore one just above my knees), shirts, jackets, blazers, jumpers, jeans (maybe not ripped) etc is acceptable.