I'd pull her out of school. I had this with my DD (now 17) She seemed fine at primary school but hated high school from the outset. She started there in 2020 which was extra tricky with Covid. She joined the drama group and seemed to settle in the 2nd year.
3rd year was beset with physical illness as she has very heavy periods and she was anaemic for a long time. So we were back and forth to various appts to help her there. Additionally, she started with migraines.
However, she seemed to have a group of pals to go into town with and enjoyed clothes, make up, music etc.
And then, start of year 4, she took an overdose. We really did not see that one coming.
Initially, we thought it must be due to her bad migraines and awful periods (by now she was on the pill but still with bleeding and pain)
But, the picture kind of cleared enough for us to realise she needed an autism asst. Unfortunately, Camhs were as useful as a choccy teapot and discharged her after 3 pointless appts.
She managed to complete high school and did well in exams but no way could she have continued there. She left in May (on study leave, just returning to do exams) and started college a month ago.
She seems much happier already out of school. And we have just started the process of getting a private autism asst.
My DD could not stand the lack of discipline and out of control classes at school (obvs that does point to autism) and the time wasting caused by mixed ability classes. Some pupils could barely read, others were very disruptive. Some weren't even being entered for the exam. Teacher abs high.
Even with hindsight, honestly there was no outward clue our DD would OD. The evening before she'd been watching Bake Off with us and chatting animatetedly about meeting up with her pals in the hols. She had a shopping trip and a camping out teen party thing planned. The next morning, she got up, got her school uniform on and took an OD. You just never know what goes on in their heads.
Certainly, keep all meds safely secured is the lesson i learned. I can't even pass on anything useful about communication. Obvs i am shite at it as i am at home all the time and DD and i were often out together - it's not as if no one was there to talk to.
School is so stressful. I offered DD the chance to come out right away but she was determined to stay and sit exans. I think knowing she could leave straight after got her through it.
All the best to you and your DD. I don't intend to alarm you but please do keep meds out of sight. My DD had no self harm history. No cutting. No eating disorder. Nothing. Still doesn't. Just an impulsive act under extreme stress caused by school.