She isn't just field shy then!!! To be out in front by 5 lengths and stop only means one thing, she is not chasing!! There are too many unknown factors here to make a judgement , age?? temprament?? how did she break in?? training methods being used??. If you really believe that she is a quick dog(I know nothing about Taree) then I would not wait a minute longer and either get her re-educated by a reputable breaker or get her to a likewise trainer who then has the experience to make a informed assesment of her, good luck!!