I think that in the same way that MOC women/butches know that they are not girly girls or feel very feminine or can't relate to the perceived feelings; femmes just "feel" it.
I have never questioned that I was female. It never felt foreign to me. I just "knew" that I was a girl and I have always liked that.
I never really integrated femme with female until I fell in love with my long-term ex.
She was very butch and heard sir pretty much everywhere she went. She did not identify as male nor felt uncomfortable in her MOC lesbian butch skin.
I met her in NOW in the mid-70's and was always, always, attracted to her but really did not understand why. We remained friends during my first relationship with a woman. I loved that first woman dearly.
She was very femme. I admired and loved her feminity but the sexual attraction was really not there. She was my bestie but we were both questioning our sexuality and fell into a sexual relationship. I also want to add that after we broke up; all of her girl-friends were butch...
When we broke up, the butch asked me out and we were together for 19-years. She came out in the 60's, when there were much more rigid roles. She was trained by a mentor in the ways of butch and recognized and appreciated the femme difference in me.
We were ying and yang and it was a real sexual spark for us.
She helped nurture the internal femme in me. I don't wear heels or dresses any more but those are externals and really have nothing to do, IMHO, with the internal identification as femme.
I went out to lunch with a butch dyke that I work with last week. She is questioning her gender identity but for now, still identifies as she/her so, I shall, too.
Somehow, we started talking about butch and femme (that is her chosen and soul dynamic also) and we were talking about butch and femme as we were driving. She always insists on driving. Surprise.
Anyway, i said something about being femme and was trying to explain it and she laughed (a quite hearty laugh I might add) and said:
"Yes, I know that you are femme. There is no question about that".