Please notice that without exception, adjectives used to describe your appearance are positive: Cute, adorable, pretty, awwww, etc. Except for the occasional "looks like Dad", which is usually meant in a good way, there will be little criticism of your appearance for at least a year or two. But then folks will start to notice the brand of the footie you choose, whether your ears are pierced or tattooed (people still DO that), if your body is properly proportioned, your eyes set apart by a nose from a catalogue, and the length of your fingers and lashes. (Be glad your not a boy.)
Here's what I suggest: Keep your body in the condition that allows your brain to function it's best (listen to it), and ignore standards set by others as to roundness or lankiness, BMI, height/weight, uber-condition or sexiness. Dedicate time to activities that keep your body strong, without abusing or neglecting it. Eat some of everything, and not too much of anything. Avoid violent sports, and wear a helmet. (Sorry, off topic.)
The body your soul wears now is the gift you were given. Be grateful for it, even if sometimes it seems flawed (and it will). You could do worse. Wait until you see what some folks deal with without letting it kill their spirit. Your grandmother curses every time she needs a step stool to access the top shelf, but at times her bigger friends wished for her smaller frame. There is no perfect body, no matter what airbrush artists believe. You can sculpt yours naturally to some extent, and artificially even more (reference my tattoo letter), but my preference for you is to to be confident and comfortable in your own skin, which, I'm guessing, is quite beautiful.
By the way, never trust the "honest" opinion about your looks from older close relatives. Their judgement is glazed by their agenda; your promise and your happiness. Always consult a sister, or a jealous true friend, if you think your eyebrows are bushy or you don't wish to go to prom with an inappropriate stain.
Speaking of clothes, in case you're not already aware, they're required. It takes a strong and dedicated person indeed to go through life without them. (There are careers and occasions that allow you to "slip into something more comfortable" occasionally, but that's another letter.) The bad news is that the rules for wearing them are myriad and fluid. Nobody has ever learned them. Everybody laughs at their yearbooks.
Now I'm no 'fashionista' (why are you laughing?), but I do have a guideline that might help; Learn the classical rules of fashion and operate within them, except where it's more fun not to. For instance, 'Winnie the Pooh goes on the OUTside' is a dictum of long standing, to which, in my old age I've added, "except on Thursdays", unless, of course, the Winnie decal is uncomfortable. When uncomfortable clothes are worn, they are called costumes, and are used only for short duration and for specific purpose. If costumes serve a utilitarian function, like a weather shield, or carrying weapons or tools, they become "gear", but can be costumes nonetheless. Costumes are sometimes necessary, for professional functions, etc., but view them as means to an end. When choosing between a bunny suit (fun) and a formal gown to wear to an awards ceremony (you'll have plenty), consider whether acting an idiot or furthering the career you've chosen is really the more fun. I've always struggled with that.
I've also struggled with body paint, including makeup. I can't help you there. Some folks use up huge parts of their lives with it. Some allow others to poke holes in their body's protective layers just to decorate themselves. There is a kazillion dollar industry selling nail paints, and face cake, and hair whitener, and tissue siphoners, and pre-destroyed jeans, and gear to pretend they're someone they're not. I have no doubt you'll be involved to some extent. All I ask is that you think before you allow someone to advertise on your rear end, that you value the resources you dedicate to fashion, and you have fun establishing your own confident, purposeful, comfortable and healthy style.
Meanwhile, I'll type a tale. You do the same. K