What you are describing is a trauma resposne... you are neglecting yourself, and not caring for yourself, because you have internalised the devaluing of yourself that your terrible monster of a woman has done to you. She is really not worthy of another moment of your time. Your grandmother colluded with her to harm you, so you have shown love and loyalty to both of these very very unworthy women.

I find it helps to clarify myself, if I ask, were a stranger to do x to me, would I accept tit ? If not, also don't accept it from a family member.

Please open time , nurturing yourself , doing wha makes you happy and brings you peace and strength. Reach out and make new friends... we all need people around us who are caring and nurturing and who are capable of reciprocating the care we give them.