So, Eilish:
1 - Always make sure your bra fits you properly. There is nothing worse than an ill-fitting bra that gives you the appearance of 4 boobs.
2 - A tank top that comes with a bra built in is not acceptable if your boobs are bigger than a B. Given you lineage, I see no bra tanks in your future.
3 - Let's just say no to thongs right now. We can revisit when you're old enough to vote.
4 - It's best to wear make-up that gives the appearance of no make-up, so skip the lip liner or bright eye shadow. It's not cute and you may end up looking like a hooker - the truth hurts my love.
5 - Try not to touch your face during the day or pick at any pimples you might have. It leads to scars and scars are forever.
6 - If your shoes hurt when you put them on, chances are they will hurt all day so bring an extra pair just in case.
7 - During your lady days try to stay prepared. Have everything you'll need in case of an emergency with you in your purse/bag etc.
8 - Don't slouch.
9 - You are prettier than you think you are.
10 - If you're with a group of friends and they are 'acting a fool' don't feel like you have to along with them. It's fine to laugh and appreciate their foolishness but you don't want to be the person who feels like you have to outdo everyone. You don't have to be the loudest.
11 - Just because everyone's doing it, doesn't mean you have to. You don't have to be a killjoy but you also don't have to be 13 years old planning how wasted you're going to get this weekend. In my experience, peer pressure is a crock. Kids who want to drink at 13 want to drink it all and won't call you a loser if you don't. And if they do, whatev - when you're 19 these people won't even be your friends anymore.
12 - I don't care about what you want to do with your hair but if it's going to be long, it has to be clean. If it's going to be colored it should be done professionally so it's not green.
13 - Let's try and limit piercings to ears for now because the healing process of an eyebrow ring ain't cute.
14 - It's OK to be a kid once in awhile. You are going to feel some pressure to grow up fast because girls tend to mature faster than boys, but that doesn't mean you have to try and be an adult. It's hard enough being a teenager.
15 - If you keep making this face, you're going to have the same wrinkle above your nose as your Mama: