My son was killed, grndma died yrs ago, mom is upset cuz I didn't go to cemetery to visit gma as I do 4 son

my grndma always said that our love ones live in our hearts, that was my belief that is why i didn't go to the cemetery, now my son was murdered a sudden death, I greive for his lost alot different from my grndma. my mother tells me I'm a selfish monster, My question is she right? my mother tells me to stop greiving for my son that I must go on. answers needed!