Gender identity != (that's the does not equal for the non-coders XD) physical sex/genitals
on the subject of whether or not she should tell people, I think it's like any other part of yourself, you should be able to be 100% yourself with someone you truly love, but I don't think you owe it to them, like you would STD history etc.
For example, I have family issues, and I want to be able to share that with someone I love; to me that is equivalent to the sharing that you are transgender. And yeah, i get the whole it's-obvious-when-you're-nekkie if you're not transsexual, but not all relationships are sexual ones.
My girlfriend who I will call Christie though is feeling a lot better and she has a date today with another transgender girl who seems really cool!