My 12yo DGD has begun experimenting with make-up at home too, with her parents' supervision and permission which I think is a much healthier attitude than my experience in my early teens, when my parents banned any kind of make-up on principle as they were very old fashioned and strict. I just got round it by sneaking it on when I was out of the house, with some pretty disastrous results. Panda eyes, caked-on powder and chalky lips! And spots galore from blocked pores. My mum was of the "soap and water was good enough for me" school of thought, but I suffered from very bad skin due to cystic acne, which my mum didn't "believe in" so I just had to get on with it. I had years of terrible bullying at school as a result. I've never forgotten it...
My DGD has some super-natural mascara that hardly shows (she hates the look of "spider eyes"), a bit of tinted lip balm and, for special occasions such as family get-togethers, very neutral chubby-stick eye shadow.
She has just started getting a few teen spots and is naturally concerned about them. For her birthday a couple of weeks ago, again after consulting her Mum, I bought her some Clinique Mild face-wash and a super soft face brush, no harsh chemicals or oil-strippers. I think it's great that her Mum is willing to engage with her and offer her support rather than ignoring the fact that she is a growing adolescent and leaving her to her own devices with the risk of her going down the route I took.
Girls these days grow up far more quickly than we did, both physically and emotionally. GD has been having periods since the age of 10 - however much her mum would like her to stay a young child forever she quite rightly acknowledges that she is now becoming a young woman in her own right and would rather she had sympathetic guidance and advice than the outright hostility and obstruction that I experienced.