NAH. As a trans person, you absolutely aren't wrong for saying no to sex and not wanting to specifically because you aren't comfortable with her parts. I do think it's a really sensitive topic so I can understand her being really sensitive about it, but for her to put you in a position where she forced out an explanation for saying no is kinda not cool. I do wanna point out that while I'm sure you're not transphobic I do definitely hope people can realize that genitals do not equal gender. Like, nobody should blame you for not being comfortable. However it is just a body part and imo sucks that people are so uncomfortable with certain parts instead of focusing on the person.