I personally think you could have excused yourself - she may well be worried over you and blocking her from your facebook etc may only increase that concern. I would at least let her know you're ok and if you could, just be honest about what happened and that you would like to just continue things as before. What if this sort of thing happens again? Will you drop out of another group? Also its unlikely you won't ever see her again, especially if you live in the same area. All im saying is that it might be better to explain now while you have the chance rather than run the risk of it having it sprung on you if you do bump into her again. Just my thoughts.