OP if your daughter is in the British system there are a host of schools which offer that curriculum: GCSE etc. Also US, Canadian, French Bac, International Bac, you name it, it's here. Kids transfer in and out of Dubai all the time so teachers are well used to helping kids to adapt and catch up.
The standard of education is higher than in the UK in general- the kids are expected to achieve more. Your daughter might have to work a bit harder to catch up the first year- happened to the 13 year old daughter of friends of mine who moved here- but that's not necessarily a bad thing. Some schools are more academic, some more sporty. Another friend of mine transferred her (Australian) boy to a different school because their emphasis was more on sport. Really, there are some fantastic options here.
The advice to send her to boarding school is ill-informed since she can follow exactly the same curriculum in the UAE- after all she'd still be changing schools, wouldn't she? As for living with relatives while you and your husband move here, well, that's just nonsense. I interact all the time with people who have just moved here (newbies at work). They bring kids of all ages. It's a bit of a hassle at first and then generally everyone settles down and loves it.
Perhaps try a dry run? Many companies here will pay for you and your family to come out on a "recce" to see how they like it.
Oh and if by any chance your husband is a pilot considering coming to work for Emirates, don't hesitate for one second to get you and her on that plane. The EK pilots really get the most wonderful packages for all the family! Plus she'd have practically free flights to go back and see those friends whenever she liked!