STOP!
Probably the best suggestion I can think of at the moment is, hold your horses! Christmas isn't here next week, or even month, it's at the end of the month after that, so you and your daughter have plenty of time to do some research, have a good think, and then (hopefully) buy a camera and lens (or perhaps a couple of lenses) that will be right for your daughter and last her a few years.
Don't worry, I've been there, I can remember when I was 15... and that was more years ago than I want to admit!
Anyway, I was very much into photography and was using an old and obsolete SLR film camera that was a hand-me-down from my Dad. Like your daughter, I wanted a new camera and something I could buy some additional lenses for (when I could eventually afford them).
So I weighed up my budget and worked out what I could buy for my money. Then I did lots of reading of reviews (buying camera magazines with some of my Saturday job money - these days you can find all the camera reviews you need on the internet free of charge!), and I worked out the most suitable and best specification camera that I could afford. Only once I was
sure I'd made the right decision (and saved up enough money) did I buy it... I still remember going to the shop to get it!
So do take your time, your daughter has a good mother who wants to help her buy the right camera so I hope she appreciates this and doesn't push you to rush in and buy for buying's sake. If she wants to be a good photographer she's going to have to work hard to learn the craft, and that journey starts here! Your joint mission is to find the best camera you both can for the money you have available.
Have a look at different makes and models, read any 'independent' online reviews you can find about them, and remember the various pros and cons.
As a starting point, I don't think either Canon or Nikon make bad DSLRs at the moment (it tends to be something like a game of leap-frog between them as to which model is best at the time) so either of these makes should do the trick. As has been said in the posts above, if she's already used to a Canon camera, the menu and controls on a Canon DSLR might be more familiar and easier to understand, so maybe start with researching affordable Canon DSLRs?
Beware of scams though, if something is quite a bit cheaper than you've seen it at a well established retailer like WEX, it may well be too good to be true. There are also grey imports (Google this if you don't know what that is) selling stuff cheaper, but it doesn't usually come with a manufacture's guarantee in the UK - although some grey import retailers offer their own guarantee, but you'll only find out how good this is if something breaks!
You might be able to get a better spec camera if you buy
second hand, but once again, is the seller reputable? Also, you won't usually get a 12 month guarantee (perhaps just 3 to 6 months) and quite often camera repairs tend to cost 100s rather than 10s of £pounds if something goes wrong after the warranty runs out!
So there you have it, don't rush in, take your time, weigh up your options and ask any questions you like once you and your daughter have done a bit of research and narrowed your choice down a bit. I hope this has been useful and helpful and I wish you the best of luck choosing the right camera.