Well, these two panels make me believe that JinMom assasinating her son wouldn’t be as simple as we may assume. Take a notice that she seems to pity him - she probably understands that this is not his fault that he participates in his father’s murders. He is too little to comprehend it.
She may think that if she were more careful about choosing her husband and cared better after her child, Jin wouldn’t be involved in this bloody shit. The milk is spilled and she knows she can’t just go back in time.
She perhaps tried to kill Jin in order to protect his mentality beacuse growing up he would understand all those bad things he was doing. She wanted to save him from becoming ruthless murderer. It was all she was able to do for him - beacuse it was too late. Too late to fix anything.