Stonewall's definitions below in italics, my comments in non-italics.
Gender – often expressed in terms of masculinity and femininity, gender is largely culturally determined and is assumed from the sex assigned at birth.
A lot of what is culturally imposed on me in the name of femininity is the oppressive shit I've spent my whole life trying to escape from.
Gender identity - a person’s innate sense of their own gender, whether male, female or something else (see non-binary below), which may or may not correspond to the sex assigned at birth.
Note the weaselly slide from "masculine" and "feminine" in the definition of gender to the biological terms "male" and "female" in the definition of gender identity. I don't have an "innate sense" of which biological category I am; I simply am that category. Nor do I have an "innate sense" of my femininity - it's just a word used to apply to a bundle of characteristics which some parts of society tell me I ought to have because of my biological sex, but which, for the most part I don't have and don't want to have, because sex stereotypes are a crock of shit.
Cisgender or Cis – someone whose gender identity is the same as the sex they were assigned at birth. Non-trans is also used by some people.
Having established that I don't have a gender identity, and that I experience gender as something oppressive done to me from outside, I think it's safe to say I am not cis. I am just a woman - in virtue of my biology.
TL:DR
I can't speak for all women, but fuck off with the "cis" label as far as I personally am concerned. I am not going to "identify" into my own oppression.