Its elementary dear Watson..... Sorry I watched Sherlock Holmes last night. I deduced Nicky's gender through body language and mannerisms, as well as facial features and expressions which are clearly on the feminine side. Also the way Nicky talks to and addresses Daniel. All these factors combined lead to the conclusion that Nicky is female or at the very least identifies as female.
Its elementary dear Watson..... Sorry I watched Sherlock Holmes last night. I deduced Nicky's gender