being constantly terrified that your friend will start to behave like she used to again might not be the best feeling to enter a friendship with. people can certainly change!
but you are not required to witness or help with that change and you are not required to give them a second chance
if you have too many bad feelings, dont beat yourself up for not talking to them! its ok!
and if you want to give them another chance maybe make sure you have a strong support group of other friends