i dont think anyone has said taking your kid out into the field is wrong,its the amount of time,ie every weekend for the whole weekend thats the problem,to be honest,by the time she is 16/17 i would bet a large amount of money that she is sick of birds and being made to follow her parents obssesive hobby.
From the age of 12-15 i was marched up and down the country to play badminton for my county much in the same way she was,yes i was good but by the time i was 15 i had missed out on so much,things like playing football,birding,spending time with mates.
The problem isn't twitching its the obsessive nature of it,its fine to do such a thing if you want to do it but if you are being forced to do such a thing when you don't really want to the majority of the time then you will revolt against it.She may really enjoy it but the odd comment from her suggest otherwise