DD, 7 just returned from 10 days with her 2 girl cousins, one is 11, and she was in charge of "watching" the 2 younger ones, my DD included. They played video games, watched videos on You Tube, including something called Chad Wild Clay (some spooky older) guys in masks, and she is doing provocative dance moves, asking about getting TikTok and an I-Phone (!) -- and she also asked me if I have my period since the 11 year old told them about this also. Is this normal ? I have a 3 year old too, so I'm not accustomed to the influence of older kids yet.

I would say it's the influence of the older cousins. I have a just turned 10yo DD/entering 5th (she's young for grade) and 8 yo DS. 10y started to ask about phone usage etc at the start of this school year--namely b/c many of her friends were using regularly (including tik-tok). All of those girls had much older (e.g. 8th grade on up) sisters. We are letting her use an old phone for text (monitored) and facetime---but hard no on tik-tok. Our 10yo is aware of her period (probably more b/c she has that American Girl book about puberty, and we talked about it). I know that there had been some talk at school (this year, don't think in earlier grades) about breast development but not sure if they talked periods.
My oldest is 8, a boy. The girls in his class seem to be on average more mature, though my DCs know about me having a monthly period, that's not something we hide. But the one with the provocative dance moves and asking for a phone is also the one with near unsupervised access to media. Seems like that might the root? Did anyone watch 11yo?