
Hi :)
You're having a bit of a time of things by all accounts but fear not, we've all been there before and many will be again!
At 7 months she's still pretty much a baby and with the best will and experience in the world, she's not remotely unusual for being unreliable on recall ;) Training is only ever as good as the lack of irresistible attractions that abound with a youngster - the opportunity to chase off after a moving object is clearly winning over any treats you may have and if she also has the enjoyment of you in hot pursuit of her the game has become even more worthwhile.
The chase instinct or prey drive can be quite marked in some breeds - although can be so with any dog of any breed - and needs to be put to use towards something infinitely safer than moving cars, runners, cyclists, horses, basically anything that is outwith your control. I'm guessing that as you have your own land for exercising her she has had much of her training done there too so there have been very few distractions during training for you to overcome? It's worth going along to a training class where she will be doing her obedience exercises with other young dogs present and where you can both slowly but surely learn to work together and keep focussed on one another regardless of what's going on around you.
Youngsters quickly pick up on things which amuse or frustrate us so in the meantime I'd avoid letting her have the opportunity to take off on her own agenda. Perhaps until such times as you have a training class place booked and organised you should exercise her on a long line so that you can safely reinforce commands and break the cycle of her chasing off after things. Have particularly tasty treats that are not part of her regular diet such as roast chicken or cooked liver/kidneys - keep high value rewards for training alone. Introduce her to a toy which she can chase and retrieve - it may take some time to find one which really gets her going but it's definitely worth puting in the effort at this stage :)
>My inclination is to be cross, mainly through my fear of her being injured, although I realise this is not going to encourage her to come to me again!
Great! You're completely on the right track here :) Infuriating as it may be, we all have to grit our teeth and sound chirpy even when we want to strange the little blighters because we're soaked through, loaded with the flu and running an hour late for an important meeting :rolleyes:

:D Take some comfort in the fact that you're definitely NOT alone!
Oh, and just when you think you've covered all the bases, along comes puberty and we're back to square one

regards, Teri