Hitting her was wrong, and you do realise it. But since you said "but lately, I've been pushing her or nudging her", you need to ask yourself if there is a slight chance that you would repeat this again? If the answer is Yes, you need to go to her..and tell her that you're going to a psychiatrist/counsellor right now and that it'll never be case again. I do realise that you are regretting your action but most of the regrettable actions that we take are in 'the heat of the moment'. And this is what needs to be cured, unless you're confident in your willpower that it won't happen again. You need to make her feel safe no matter what.. if it means going to a counsellor or doctor, then just do it. Follow up on your words.. Merely feeling regret is not enough.
I personally went through this phase too where whenever someone insulted me, I slapped or shouted or hurt them no matter how important that person was in my life. But I later realised that I had lost too much due to my anger and decided that Enough is Enough and this needs to stop. I tried controlling my anger and anxiousness through sheer willpower and it has worked wonders for me. Yoga, Meditation and A running session helps my mind to clear out and releases all stress. I hardly feel anger these days, and its safe to say that my life has changed for good. You might as well try 'em too, it might help. And as of now, I believe you need to tell her that this won't happen again and follow up your words with some stern action.
