A pattern is made of paper, pinned with the seams outside. Put it on with care, adjust the fit, trim, leaving 1/2" past the seams. Pin the paper to cloth, consider the warp, all facing the same. Adjust the fit with pins, when it is right, baste with 1/4" stiches, loose so the cloth lays flat, Ask nana about machine sewing.
It used to be a common art, still a lot of machines around, and some who sew. No one is born knowing these things. Those who know will help you.
It is a real interest, a girl thing, and I think nana cares about you. Parents are generally hopeless, they carry the burdens of the world, their lives, and children. They are overloaded and often stuck in the mud.
Nana is past a lot of that, Member #1 of the RedMage Fan Club, and if you ask her if there were girls like you when she was growing up, there most likely were. They are also likely still around.
My grandmother told me that when she was a girl she carried an eight inch hat pin. Stories of girls with knitting needles were common. It was a bit wilder in the old days, girls had to take care of themselves.
Now you would be taken out and hung, but nanas group were your age when all those American troops were about, and they do have stories.
Older people have a different point of view. My girl is eighteen. When she was little, and listened to me, I told her she had to obey me, and when she quit giving me a dirty look, I told her that she had to do whatever she wanted, because it was her life and I, and no one else, could live it for her. She has always obeyed me, above all others.
With you, first you have to find someone you would let in your personal space. Nanas are not a threat, and once were girls playing with dolls. It may not be your nana, but there are others, and they were girls once.
Outfiting you as RedMage is playing with dolls. You will have to stand for fittings.
Ask nana about girls like you in her time. They got away with it. You can learn from people like you. Not much to learn from children, parents are a lost generation, but in the company of nanas, you could find proto-Mages. They tell stories, know how to sew, and make the best cookies.