@Grunt
The issue here isn't her not making the potions "so OP", but the fact her power is too hard to control. if you make a potion that can "save a life", it will save any life, from any kind of danger, in any possible way. It's kind of like the tale of the monkey's hand -I'm not sure if it's the right name-, be wary of what you wish for, for it will be granted in some random way, the limits must be set by the person making the wish.
Just think about it, how can you verbally define something so it does exactly as what you're thinking? And then try to find any loopholes to that which you thought of, it's insanely hard, and almost impossible to not make an OP potion with that sort of power unless you think about something that already exists, such as the soft drink.