Alright, time for the captain to step in. Bitches gettin' out of hand.

I'll put it in a more polite way; that's not really a valid explanation for Quinn knowing that Theresa was transgendered from one look when there are actually [i]countless[/i] variables in this situation. There are girls who have rather masculine appearances. Quinn doesn't know Theresa from the rest of the lot, I think that's a stretch with how little information Quinn has about Theresa. What I would have done instead is silently note that Theresa is rather masculine, or not like other girls (Special snowflake, ya'll). Since there isn't enough for Quinn to make that connection. 

I'll have to say that Quinn shouldn't know Theresa is trans. But, since Quinn's question was pretty vague, I don't think you have to edit your post.