This girl wears tightish skirts which barely cover her knees
She should say that and let the person she’s speaking to decide if that is tznius enough or not.
I usually tell people that I don’t answer open-ended questions
Basically, you should just say you don’t give information at all. Because you’re really not giving any information. Like you said: everyone is somewhat tznius. Everyone is also somewhat smart. So really, the information you give is not worth anything.