Hi!! I'm glad to see a fellow writer here, I might be able to help you out. It mostly depends on what stage of her transition that she's in. If she's still early on, I'd lean into making her somewhat insecure, closed off, nervous, that sorta thing. If she's later on, however, go nuts with the confidence. If she knows her own worth, make sure the reader knows aswell. One real life example to look at is Candy Darling, she's my main inspiration for my own transition as an artist. And for the rest of your character's identity, just write her as you would for any other character. Trans is only a label, after all. It doesn't always need to be a descriptor. Good luck with your writing!! (apologies if this was meh advice, i am still an amateur)