Does anyone know how to get over being bitter with the mother of the one who murdered your daughter?

I share co-parenting with her after the murder.we have 2 grandchildren that we share co-parenting time with.(not my choice)I have to deal with her all the time.Right now we are not on speaking terms.She always has something new to upset me with.I also have 2 other grandkids that we have already adopted.