Hi Colacard, you mentioned she's had lots of tests - do you know if they checked for coeliac? I had umpteen tests and scans in my early twenties but they didn't find anything until 8 years later, at which point biopsies showed coeliac disease in final stage. Hopefully not the case for your daughter but it is more common for diabetics and somehow gets overlooked time and time again.
Referral time will depend on your area - our area has target of 12 weeks but I think it was slightly less than that from getting positive blood test to getting endoscopy (camera down throat) then another 2-3 months to see gastro.
Hope it doesn't take too long. Might be worth calling hospital to see if you're on their list, and mention you're flexible for last minute cancellations etc (if that's the case!)