Well, "a women" isn't anything. "A woman", however, can be many things. There are no "rules" you need to fulfill to qualify as a woman. Most women were born female but that's certainly not the only way to be a woman. A lot of women have long hair but you don't stop being a woman when you cut it short. Some women like to wear dresses, some don't. What matters is, does a person feel they're a woman or not? Of course, if there are no strict rules how would you know? But since our society keeps insisting on certain classicly male and female attributes you might feel more strongly connected to some of them than their counterparts. That still doesn't mean you have to embrace all traditional gender attributes at the same time or even most of them. If for you the only attribute that makes you a woman is having boobs and you have boobs you can call yourself a woman and it doesn't matter if you have short hair, wear dresses or even have a beard. Just keep in mind that not everyone's defining feature is the same as yours.
I, personally, could really do without the definition of gender because to me people are people. Gender does not define who I am attracted to - there are far more important things to me. I don't care about my own gender - call me a man or a woman or whatever you want. But as long as our society collectively needs to make this distinction and if it is important to someone I will respect their pronouns and identity as soon as I know them.