My son is only 8... So maybe you'll want to take my advice/opinions with a grain of salt... but I was a pretty rebellious teen, so, I feel like I can speak on the issue.
My first thought/concern is the body mod/suspension stuff and is it all clean!? You say it’s at the discretion of the artist, but I’m wondering how legit any body artist who is willing to deal with underage kids is, you know? But I’m in the States, so maybe things are a lot different, I don’t know. But yeah, I’d be talking to her about the health risks that are involved when dealing with someone who may possibly be questionable. I have nothing at all against body modification but it’s got to be clean!
The clothing- Not a hill worth fighting & dying on at all, IMO.
The sex- I would definitely talk to her about having respect for her body if you haven’t already… but I’m of the mindset that if teens want to have sex, they’re going to. You may not like it, but you can’t really stop it. Do what you can to make sure she’s staying safe!
School & suspension- I could totally see myself punching some boy in my teens for being disrespectful! If his hands were on her he was sexually harassing her! I hope he was also suspended! As for school in general, I HATED IT! I ended up dropping out

I so wish my parents had taken me seriously enough to give me another option other than “just go to school!” Is there any way you’d consider homeschooling? Unschooling? If she hates school at her age, I really don't think this will change... so looking into another option would be good.