Hi marbles. Sorry you are going through this. My DD started with panic attacks in year 11 (yr 13 now). We were all at sea and felt very alone, not knowing what to do. She was off school for three months, and at her worst could only go out very locally - no buses, trains, shops, cinema, long journeys. The good news is she is able to do all those things now and the panic attacks are few and far between. It took three months to get back to school part time, and probably about six months to start feeling much, much better and able to cope.
Whilst waiting for CAMHS I downloaded a booklet by 'Moodjuice' (just google it - social anxiety) and gave it to her to work through herself. This may work with your daughter if she's refusing to talk to you. It did help mine. My DS1 had something bad happen to him at uni two years later and suffered PTSD. Moodjuice did a booklet for that too, which he found helpful. In both cases I just gave them the booklets and left it up to them to read/work through in private.
We had two different experiences of counselling - hers no good, his brilliant. So don't put all your faith in it but fingers crossed you get a good one. May I also say he engaged much more than her, which makes a difference.
Re: medication. None for DS and he's fine now. DD had beta blockers for a flight abroad, which worked well. 3 months ago she asked for medication as her panic attacks were getting worse again and she felt very low (17 yrs old by this time). GP put her on Citalopram. We've had a long battle with excessive tiredness, but she seems to have come through that now and they've helped enormously.
Other than that, we tried to remove all pressure from her when they first started. Told her she didn't need to pass her GCSEs, study at school (home instead), go anywhere she didn't want etc. I've no idea if that was right but bit by bit she eased herself back to things. She learned to recognise what the panic attacks were and deal with them (breathing techniques, removing self from room etc)
Sorry for the long post, I hope it helps a bit. You're not alone!
PS. We never found a 'reason' for DD. People often ask why, but I don't think there necessarily is one.