- Undergo hormone replacement therapy (hopefully under medical supervision).
- Undergo non-surgical, non-hormonal procedures to mitigate the effects of testosterone, e.g., facial electrolysis.
- Undergo surgical correction of the genitals (and possibly other surgical procedures, e.g. tracheal shave).
- Live the life she should have been living since she was born.
Simple, yes? Not cheap, and not easy, but pretty simple. There is no need to make it complicated.
Girls who start hormone blockers early enough can even skip some of the above, since they will not have to mitigate the effects of testosterone.
Notice that there is nothing about how a person dresses or acts. Some women are very feminine. Some are rather masculine. Most are somewhere in between. But they are all women. Most women dress and behave in a way that feels natural to them. Girls as they mature learn what it means to be a woman. And they learn who they themselves are.
If you were born with transsexualism, then being a woman is just that—being yourself. If you are a woman, that's what people perceive. If you're making a lot of effort, there might be a problem.