A lot of us will say gender is like a bone. You don't feel it until it's broken. As a man, you've never ever had to question anything, and so your gender was just THERE, not to worry about. For trans people, it's like we've always had this broken bone. It's been that way for so long though, the pain became a bit dulled, and we got used to it. Doesn't everyone have a broken bone? Turns out, as we grow older, that no, that bone ISN'T supposed to be perpetually broken, and we need to fix it best we can.

If we want to actually look at biology, your friends brain, as well as mine as trans women is NEARLY IDENTICAL to a cis woman's brain. So she's been living "as a boy" this entire time, with a girl brain inside her, telling her that her body is supposed to look like a girls, but it doesn't. That brain expects breasts and a petite body, soft skin and a soft voice, and instead she's rewarded with muscles, beards, and a penis. She closes her eyes and expects the body and life of a young woman, and instead some strange man's body that is not hers stares back at her. People see that body, and even though she's a girl under the hood, people treat her like a man. How many other women would like being treated like a man? Exactly.

Now can you imagine how confusing and painful that might be for her? At the very best, trans people have strong support systems they can rely on. At worst, there's a 40% suicide attempt rate in the trans community, due to that inner pain, as well as transphobia and hate from the outside world as well. So the best thing you can do is be supportive of her, even if you don't understand it fully, and help her where necessary.