Best advice I can give you is to find a good trainer. Horses who breed true to the temperament of their lines, you want them to get a good start from day 1. If they are ever allowed to start dumping people on purpose, then you'll just be stuck with something unrideable.
Something to consider...you spend the dough to get her trained only to find out that she's a little too much for you. With her lines, if she's built well, you could market her to a ranch/cowboy market and, if her training is good, then she'd be worth a pretty penny even with a sensitive temperament. Because she's a mare, she'd also be worth more than a gelding due to the possibility of being a broodmare...if her conformation is good.