My dd is 8.
She has always been happy to read, not an avid reader particularly, but neither did she moan about having to read her school books.
Now, and since she started back in Year 4, it's like pulling teeth! She really doesn't want to read anything, not even her own books. She goes between flatly refusing, acting like a 2yo throwing herself around, and everthing else inbetween 
She's a good reader (was assessed as a 4C at the end of Y3) so it isn't that she struggles. She's just taken a massive dislike to it 
Any ideas as to how we can avoid more tantrums encourage her to read again?