Here is a personal story. My uncles horse, Chumly, was worked in hand young...about 1 or 1.5 yo. This work included lunging. Yes old cowboys lunge too, although normally loose lunging. My Uncle very much believes in the same principles as I do when it comes to training, although we were both largely taught by my Grandpappy. Chumly was lunged every day at a young age along with his ground work. yes he got arthritis...when he was put to pasture at the age of 26. Even with stiff legs you can go out to him after a winter or a year, or even two, off and get on him and he will take you anywhere. He is now old and retired. He showed sings of arthritis at 24 it started effecting him at 26 and it wasnt until the winter of his 28th year that he really started to stiffen up and only the kids were allowed up on him.
I personally believe, from what I have seen even between half sibling horses that the development is purely by the horse based. However people also say that because a horse is a stud that it stunts the horses growth which I dont believe seeing has how 1) you cant have the same horse let him grow to be 16.3 and then say oh he would have been taller if and 2) you cant test it to prove it by having the same horse grow up as both a stud and a gelding to see if there is actually a difference.
At this age I would personally stick to light ground work, yes even lunging if you feel comfortable with it. I prefer to loose lunge because the horses has to learn to read your body language a lot more and sooner. Just go slow and easy. Let her tell you what she is ready to do. I would also think about getting her an exercise ball to play with or learn not to spook at. Also talk with the person who gave her to you, see what they would suggest, if they would help you with her, what they prefer for the other horses they have trained/used, etc.
At a year a horses should be halter broke, broke to lead nicely behind you and not push you, deal with things that will be around at training/breaking time (grooming supplies/kit, saddle, plastic bags, buckets, mounting blocks, etc) if she isnt already good with things like that and walking through gates while you open and close them then I would start there first, of course. Ultimately, the training (both style and technique) is up to you to choose and work out. Yes we can tell you what a study might say or how we have worked with horses or trained a horse, but we still dont know you or your horse.
She sounds lovely, good luck with her and your adventures together.
~Set Your Heart Free on the Wings of a Horse~