Is it ever ok NOT to forgive someone?

My mother has done evil wicked things to me, I have forgiven her at least 100 times and I mean really forgiven her in my heart and soul and she goes back and does even worse things....From lies to deception to outright competition and wanting me to be in pain or fail - I can't even talk to her on the phone it makes me that unhappy and stressed. I am the only child so I have tried to make it work but I really need some advice.... I can't even talk to her on a limited basis. I know deep down she is just in terrible pain and full of fear and anger but I am trying to go healthy places in my life and everything out of her mouth EVERYTHING is ugly. Even down to hearing about her own life and how much she hates herself (and yet thinks she shouldnt change anything about herself). Can I still be a Godly person and turn my back on her totally? She has made me promise I would take care of her in her old age but I can't take it anymore and I dont think I can succeed or have spiritual growth if I even have to TALK to her for 5 minutes once a month. It's that bad. I need some advice... Any other kid would've bailed by now but I am just not an a******! :-P HELP PLEASE. Tweet