In contrast to the other responses, I might suggest that she doesn't necessarily want to be your princess. And maybe she does — you know her, we all don't, and as it turns out some women are looking for certain things in their partners, others want something else. You should treat your girlfriend like the unique person she is. In that sense I agree with the other people who responded — they gave general advice on how to treat a woman you are dating, and all I'm saying is that it's maybe not universal.
What's likely relevant to her being trans is the insecurities and psychological trauma that comes along with the experience for many people. That comes up both in intimate/sexual situations and in life in general. You talk about her expressing concerns and struggles and fears, and yeah, that's the insecurity. You don't have to understand — she might do better to find a support group, where she could find people who do understand. What you can do instead is admit that you don't understand, and assure her that you will be there for her regardless. Knowing the "right" (for the time being) terminology is nice, but what matters more is feeling safe with you: That you won't misgender her, or treat her like a second-class person, that you aren't just settling for her, that you love her, etc.
When it comes to sex, well, lots of women have trouble having an orgasm, though perhaps most cis women like that don't feel as much that it threatens their sense of womanhood. You should get her a Magic Wand or similar if she doesn't already have one. You might enjoy it yourself, by the way. Other than that, again, generic advice applies: Communicate, be open, relax, don't focus too much on orgasms, etc. Again the only issue specific to her being trans is that she's likely to feel more insecure, which just means all that generic advice is more important.
