When a horse leans into people they are out of balance (and mares will push into pressure), so move the horse over. When lungeing the horse, the horse must stay between the hand holding the line/caveson, and move away from the whip (point it at the shoulder/move the horse), this is basic handling (but likely you are moving away from the horse instead of visa versa. In a round pen the handler is controlling the situation, out wise not. Will she lead and stop when you do (with you at the shoulder)? If not, why not? If you turn, does she turn? Are you CONSISTENT in what you ask? Basic horsemanship, little need for an over the top action, just clear/consistent actions which must be met with her consistent reactions. If not, ask what you might be missing (in timing/clarity/etc).