tranny is often used as shorthand for transsexual transgender and transvestite all of which are separate words with very different meanings it encourages the proliferation of incorrect assumptions about queer people and on the whole should never be used by anyone even those familiar with the differences would be cautioned in using it too because theyre not necessarily aware of whether the person theyre talking to is also aware of the differences you yourself used the word incorrectly to refer to a gender fluid person which afaik there isnt a specific word for yet not blaming you for that but its one more example of how misinformation spreads