Could these powers be working on their own? I see these powers as a gift - your brain is super charged - you get mad at someone and something bad happens to them. I know if you do bad, it will come back multiplied which has happened to her. If she practised just simple things like happiness, love, good fortune this too should come back multiplied and the energy that's going bad could be calmed down?
ANSWER – Couple of key questions in here and in relation to the whole concept of magic working without the specific intent of the castor I suggest you have a read of a question that has been asked before here as it goes into some depth about how magic works. In summary though, yes it is possible for a witch to cast without deliberate intent, it tends to be linked to particularly emotional times – anger in particular – and can be explained in simple terms of the energies aroused by the emotions being subconsciously directed into what is on the mind of the person raising the energy.
I’m interested that you consider your friend a witch yet say she doesn’t practise witchcraft. I have to be honest – someone who doesn’t practise witchcraft is unlikely to do a great job of being a witch. I think what you mean is she has certain gifts and a natural ability to manipulate the world around her. It’s semantics as to whether this actually does constitute witchcraft but whether it does or it doesn’t I agree that the results she is generating can be very real and perhaps more frightening to somebody who is unused to manipulating energy consciously.
However I would caution against being too quick to match up cause and effect. Good and bad things happen to people every day of the week. It’s human nature to look for patterns and to see anything that fits with that pattern as evidence to support it. Always approach this sort of thing with an open mind - yes it is perfectly possible she is having some influence but equally it is possible that the things that have happened to the people she has been mad at have would have happened if she had never met them. Perspective as they say is everything.
Your question states that if you put bad in the world it will come back to you. This is a viewpoint (mainly held by Wiccans) not a proven truth. There is some common sense behind it – if you go around doing nasty things to people, chances are somebody is going to get you back for it – but there is nothing suggest that magic itself is anything other than morally neutral. Theoretically a witch could spend her life casting negative magic against everyone she knows and receive no retribution at all for her unpleasant ways. My point being in this case that there may not necessarily be ill consequences ahead for your friend from what she is doing and equally that if she starts to try and counter the balance by practising magic connected with happiness there will not necessarily be good consequences in store for her either.
However that said, I do think there is some sense in your suggestion. What will happen if your friend starts to focus on the lighter side of life is that she will find her mood start to lift and hopefully become less angry and inclined to be “mad at people”. If she does try to put more happiness, love and good fortune into the world she will feel a sense of achievement and less frustration and will therefore achieve a better balance of energies that may stop her anger bursting out in random directions and going haywire.