Teen Gothic

I (college student, M) just got a text from my little sister (13 y.o.) that shows her trying out some tradgoth makeup. She's always been the preppy, Lululemon, 'clean girl' type, but not because she liked it, just to fit in. Now she's finally trying to do things for herself. And even though it's my duty as an older brother to make fun of her, I can only make fun of her if she's actually happy.

I've already looked online for some goth band recommendations and sent them to her, since goth is a music subculture, but I don't know much about anything goth-related. She's still young, so I want to encourage her to get clothing items that can be used in non-goth outfits, and I also told her to check out whimsigoth, but that's as far as my knowledge extends.

What tips do you guys have? Should I get her to read some vampire literature? What should I buy her? Eyeliner? Foundation? We're brown, so she can't do that usual white base. How does one put together a casual goth outfit that can be worn at school without getting harassed?
I'm kinda grunge, a dude, and I dress like my hamper fell on me. So any help would be greatly appreciated. Thank you!