Just have Minwu revive her and leave her at that. If she was at full HP when the battle started and she is revived from dead, the game will count that as her losing almost all of her HP and more likely as not give you a HP increase. You don't need to whittle your characters down to single digit HP every time you want an increase, just a fair percentage (I tend to find anything below a 50% drop will almost guarantee an increase).