You've gotten lots of good feedback already, but I thought I'd throw my take in the mix. I was very much the tomboy when I was little and wanted to grow up to be the Rifleman (devasted when I found out that I would grow up to be a woman and not a man... I thought I could be whatever I wanted). Anyway, it just seemed like most of the things I liked were more "boy" than "girl" and my mom tried and tried (and tried) to change my outlook and make me put on dresses and wear my hair a certain way. I hated it and thought she was never happy with me. And, I agree with what Brenda said about her wanting to hide things from you because that's exactly how it made me feel - like I had to hide my true feelings because they weren't the "right" ones.
Eventually, I began to want to more feminine things (still wanted to do most of the other things, like ride my motorcycle, hike and climb trees, etc) but I felt like I had to hide that from mom, too. It seems funny now, but at the time, I felt like it had been such a battle for so long - my mom trying to get me to be more feminine and me resisting it - that when I finally felt like being more feminine, I was embarassed that I wanted that and felt like I was "giving in" somehow on this long war and that my mom had "won". But, then, that's what she set up by making it a battle.
If I could offer my two cents, for what it's worth, just revel in her independence and wait and watch as she changes. I really wish my mom had accepted my ways because when my tomboy phase was over, I never really felt comfortable asking her for help with the feminine things that I hadn't learned when all the other girls did.
Good luck.
oh, and about the Rifleman thing... I eventually was extremely happy to be a woman, so that was really just the confusion of the 5 year old who respected what the Rifleman stood for and wanted to have that kind of strength... remember that the perspectives of children are not always what we see as adults. I didn't really want to be a "man", I just wanted to be strong and ethical like he was. Don't know if that made sense, but I hope so.
P.