My DD is 12 and sounds similar. I hope I can offer something helpful from our experiences.
First and foremost, a reminder to pray (because I need it myself!): that God would help her to embrace and love being a girl and to become the woman He has made her to be.
We've done some backdoor approaches, because I have felt like it just makes things worse to approach it directly. I've had to sometimes talk with my DD that she is just as much a girl as anyone else even if she doesn't enjoy dolls or dresses or the color pink; that that is not what makes one a girl. She can be feminine in other ways!
-Even if it's Legos, point out her feminine qualities (without calling them that) while she is playing. Praise her creativity, any glimpses of nurturing, and her unique talents in her play.
-Part of my daughter's insecurity with being a girl seemed to stem from living in the shadow of her older brother and boy neighbors. When we found some nice girls for her to spend time with, it really helped.
-Look for or start a tween Bible study with other girls, enlisting help from other moms if needed. There are some really good books you can work through together, and then do crafts, have a mom come in who is good with hair, cook together, put on a play, write stories, have a book club when you are done, etc.
-I saw some changes in her attitude when we talked about puberty together. We used the American Girl book The Care and Keeping of Your Body because in spite of her distaste for dolls, she likes AG since they are more like "friends." There may be better books with a more Christian tone you would rather use. BUT, sharing about growing up made her excited instead of scared and gave her mom as a confidant.
-My DD does not want to be a wife or mom right now, either. We don't push this subject but if it does come up from time to time, I simply ask her to be open to what God may have for her and then drop it. When hormones fully kick in, I may have a totally different battle in a few years!! Instead my desire is to model a godly marriage before her and help her learn how to manage a household...even if it is just her own, she will need that skill.
-The dresses: take her shopping for nice clothes she likes. My DD has sensory processing disorder and I have come to realize she does not like dresses because they are often uncomfortable. We've found she likes skirts, and she appreciates long ones because they are more modest. We are ok with having her wear slacks to church so long as she looks nice. Comfortable clothes was a key for her, so we go with that. We also had a "tip" on a store from a young Sunday School teacher she admires.
I hope something here helps. Your DD is still young so I do think there is a chance she will outgrow some of it, or perhaps another way to look at it is that she will grow into who God has made her to be with some loving support from you.
