I do know what I'm talking about. Anything not a full dress is by definition "short." She's not wearing a full dress, thus it is a "short dres." Specifically, it's a knee-length dress, which if it was just a skirt, would be a "miniskirt," they are the same thing in terms of length, being "around the knee," the only difference is a dress also covers the torso. "Micro" is mid-thigh or higher.
If you had just said "I don't think that's short enough to qualify" then that's your opinion, and obviously mine is it is, and no response is needed. But you said "Not a miniskirt," which challenges the validity of a dress for not being a skirt, which as I pointed out to you, qualifies by the thread title. Thus the efficient response pointing out "short dresses" is in the thread title as all was required to refute your assertion.