Never. There is never any justification to be angry at God. Whether it is through some event that has happened to you yourself, or the sickness or death of a child, spouse, or another loved one, there is never any justification for the creature to be angry at the Creator.
Indeed, while humanly speaking I understand why you may feel angry, the fact is your anger at God is a matter for deep repentance. Behind your anger is a sense of pain, and you are allowing that pain to produce an emotion toward God that will have lifelong and eternal consequences.
You need to realize that God does not owe us a life without pain, suffering, or loss, and there are a million reasons why God should be angry at you or me. Man is the rebel. Man is the disobedient one. Man is the one that God should be angry with, and if we properly understood how sinful we are and that in spite of our sin, “God so loved the world that He gave His only begotten Son” then we can never justify any anger towards Him.
He is perfect in all His ways. So repent of your anger, and acknowledge that you deserve worse.
Armen