The biggest question is what does she want to do with it?
If she is a big app user and has loads of apps that she loves, then really, you need another iPad. You can get a cheap iPad in two ways:
1) look in the Apple refurb store
2) buy second hand
If all she does is read the web, do email, and skype family and freinds, then I think a Nexus 7 would be a good choice. If books are her big thing, then why not get a tablet from the Book experts, Amazon!
Being honest though - you'll probably have to compromise your definition of "quality" if you only want to spend just 200 quid.
B.