OP, in the nicest way possible forget about the vape
A few puffs will not have harmed her.
Forget about it now. Don’t think anymore about it. The constant “will it have harmed her” “but the battery was on” questions really come across as you are panicking and thus influencing this on your DD, making her worse.
Forget about it now. It’s done with. She had a few puffs. Her lungs will be absolutely fine. We can’t turn back time.
Concentrate on dealing with the meltdown the best you can. Don’t mention the vape or her chest to her. Just reassure her that she’s physically fine. Don’t ask her questions. Don’t invade her space. Don’t try and make her do anything. Ride it out.
I suffer from health anxiety and intrusive thoughts, and I often experience heart palpitations and chest pains when I’m having an anxiety attack. It can genuinely feel like I’m about to die. I become extremely irrational.
It may be worth getting in touch with DD’s GP, or CAMHS. If she’s likely to have a meltdown in the near future if triggered by health worries.
It’s also worth wondering what are her “friends” telling her about vapes. There can be some really stupid but harmful rumours that go around schools. Such as “vapes can kill after a few puffs” and whatnot.
I really do hope she is ok and calms down soon x