Now this may just be me, but I think neck reining is generally something that anyone can teach their horse. All it is is yielding to pressure. If you;ve spent a summer working on ground manners, I'm sure she's been introduced to this concept already.
I think you are ready to at least try it. If it ends up being something that you don't feel comfortable with, send her to someone who does, but you could at least get the basics on her.
What I do is if I ask for a turn, I will ask with my leg and lay the rein on her neck like I was neck reining. When she doesn't have an idea what I am asking her for, I will add direct pressure. Eventually, I have found that they will respond to the pressure on the neck and not need me to go the extra step to direct pressure and eventually I can take it away.
Im not a horse trainer though so there are people on here that can give you a much better understanding. Me and words don't get along so well :P I just wanted to let you know I think it's something you could handle if she is ready for it. I don't think it's a bad concept to introduce to a horse at any age.