Of course, the vast majority is still the same but you’ll only end up having to look out these “new” topics when she comes to them if it’s an older book.
If I were you I’d ask the maths dept at the school what textbook she’s going to be using. Most publishers have a whole slew of books not just the one; practice books, skills books etc etc. There might be one that complements the one they provide. It is also possible that the school itself will be using a pre-2015 book themselves of course, and supplementing as required. Textbooks are not cheap!