I grew up a tomboy. I hated skirts and dresses and was raised with boys. My first "crush" (I was in 2nd grade) I'm pretty sure I only liked because he lived on a farm and had horses, pigs, LOTS of dogs, iguanas/other lizards, and peacocks. When I went to his house I got to play in the dirt outside, climb trees, and do all of the things that I couldn't do at my house.
When I was 18 I got my first skirt on my own free-will, realized how flipping comfortable it is, and was hooked. Now, I'm still a tomboy - I still have a somewhat crass sense of humor, brutally honest, hang out with mostly men, opinionated, feisty, not easily grossed out (unless there's blood and needles) - but I wear skirts most of the time. I don't *own* any make-up. I brush my hair once or twice a day, but that's only to keep it from being tangled. I don't blow it dry. Ever.
My clothes haven't changed who I am, but they do reflect a certain style of who I am (i.e. I don't wear neon colors and tiger stripes like my one of my best girlfriends does because that's not me). But honestly, if I hadn't had my mom, I wouldn't have had a clue how to do any of this. My mom I think likes living vicariously through me in the fashion world, as pretty much any time I come home she asks to take me shopping (which I still hate) and buys me a bunch of clothes. She still wishes I would get a pixie or bob cut hair cut (right now my hair's about 1/3 down my back and I love it), but if I didn't have my mom and my one girlfriend help me figure out how to do fashion, I would still be wearing jeans, t-shirts, and tennis shoes every day (which I still do pretty frequently, but I don't feel very good when I do that). I found one woman to cut my hair who was a genius with what would good on me, so when I wanted it cut, I just went and said, "I have no idea what I want, but here are my requirements [i.e. I don't have to blow dry it, because that will never, ever, ever happen]." That took a lot of bravery.
At the risk of sounding cocky, lots of men are after me. Good men, good friends, but men who aren't my type as far as personality goes, so nothing's happened. I think a lot of it is partially *because* of my tomboy-ness (although it has gone against me a few times) plus the fact that I found myself in my style and so I still maintain a bit of femininity about me. And with finding all of this about myself, I did gain a newfound confidence. It also wasn't until I went to that one salon and got that cut that I found a new confidence in my hair. I don't have the same style (actually, is the same style I had when I hated my hair and thought I was ugly), but I think my hair is pretty awesome now.
All of this to say: it's absolutely possible not to change or compromise who you are, and instead expand who you are by exploring some of these areas. Maybe approach it by asking her if she's ever thought about spicing up her life a bit by going on a whim and getting a new haircut (that haircut from that one stylist that changed my life? I went into her for a trim, and she suggested something else that met my requirements and I went with it), or something. Maybe ask why she's had the same haircut her whole life. You can be honest and help her without being brutal or mean.