I think an iPad will be more than sufficient for your daughter if her personal usage limits to what you have mentioned in the original post. In fact when iOS 11 launches, more and more people will be able to use it as a truly laptop replacement.
Having said that, I will advise you to keep the Air around if it still works, just in case she needs it for something else and also I will oppose with the people who are saying - get the most expensive iPad you can buy to "future proof" your purchase. In fact, I will suggest to take her to the Apple Store and let her try out the various screen sizes available starting from a mini to the 12.9" pro. That will narrow down your search a lot. If she seemed to like either the 9.7 or the 10.5 iPad then consider the 9.7 first because it's way cheaper and very powerful at this point. Unless she's going to use the Apple Pencil for creative work, personally, I feel the pro models costs a lot for an average iPad user.