Hello Lilah sorry you and your daughter are going through this
.
My daughter went through something similar (albeit less severe and related to slightly different things) a couple of years back, and has now fully recovered (aged 14 yrs) although we are obviously on the alert in case it should happen again.
It was when she was 12/13 yrs old and she got very anxious about travelling on the tube (we had had incidents of terrorism where we live and school had been evacuated on one occasion) about academic study (we live abroad with pretty pressured/brutal/rigorous state school system) and taking exams. She exhibited various stress symptoms such as agitation, not sleeping, worrying, being very cross and irritable and crying. At the same time she started her periods and one of her classmates suffered a sudden fatal accident. All in all, a very bad, stressful time.
We approached it by first going to gp to get blood tests, to rule out anything physical. As your dd is actually physically being sick which is quite severe and must be awful for her, I think it is worth ruling out any physical symptoms first.
Also, is she eating well otherwise? (Not suggesting this is the case, but I would be alert to possibility of fledgling eating disorder.)
When the blood tests came back ok save for a bit of anaemia and vit D deficiency, the doc recommended a licensed, clinical education psychologist. DD went to see her for eight sessions and that was all that was required to sort things out. Tbh, although the therapist was good, I don't think it was actually the therapy alone that helped the most. I think it was the fact that (a) dd felt listened to (b) she got a bit of time out from school, (they gave her permission to miss sport for eight weeks) (c) everyone constantly told her that it was totally normal to feel this way occasionally, that anxiety is very common, that she wasn't going mad and that she wasn't abnormal in any way and she had done the right thing to tell us she was worried (because I think all the stress had built up in her head somehow and she was in fact more stressed about being abnormal than about the actual stress ifyswim).
I do think your instincts are right to act on this quickly and nip it in the bud as soon as possible, as stress and anxiety can spiral quickly out of control. I thoroughly recommend seeing a therapist privately if you can.
Have you looked at the the Young Minds website ? That might be a starting point although I am not familiar with UK adolescent mh provision.
In summary, I would definitely seek help for your daughter asap. Sometimes, we all need a bit of outside support! Good luck!