There are a few things which if you do it before you ever get on her back will make her a better horse under saddle (at least easier to break).
1. Although she's young you can teach her to steer (with help from a friend) by teaching her to bend and move in the direction you want by using long reins (driving reins) or even lunge lines attached to the SIDES of her halter, and standing behind her (far enough away that if she gets scared you do NOT get kicked).
(Do this in a small confined area since you're doing it with a halter and won't be able to stop her if she gets scared.) Using this method and voice commands teach her to "walk on" (followed by a click at first and if neither of those work have helper stand by her head and lead her forward, Whoa (stop), turn left (Gee), turn right (Haw). Once she knows all that it will help her understand (using same voice commands) when you eventually get on her back. Eventually you can ditch the helper and just use the voice commands to get what you want.
2. You can teach her the start of leg yield from the ground. Start by standing near her girth area on her left side. Taking your fore finger "prod" her where your leg would normally ask her for forward while bending her neck left. The first time she may do nothing so prod a bit harder and add a click (or two).
Even if she does nothing more than shift her (hind leg) weight AWAY from you - praise her.
Repeat until she steps away from you until you stop bending her and or stop the prodding.
Make certain you do this on BOTH sides because when a horse learns on one side it does not automatically translate to the other side.