Let's skip whether people have a right to be mad at God---lot's of historical "holy" people have been mad at Him.
More importantly, feel free to be mad at God---in the first place, He is quite capable of handling our anger; and in the second, He's really great at being able to comfort us when we're feeling like that.
That might depend on whether you are one who gives God credit for good things happening.
If we go to Isaiah 45:7 -“I form the light and create the darkness, I bring prosperity and create disaster. I, the Lord, do all these things”.
(I am presuming you are a believer in the Christian God)
It would follow then that God is responsible for bad things too. You have a right, but you may find that blaming God is a futile effort, since it isn’t likely anything at all would change, no apology will come, nor will you feel any better about it.
Food for thought, Megan: About 9 million children under age 5 die every year, around the world, from things like accidents, diseases (like cancer), starvation, and abuse. Should we imagine THEIR parents didn’t pray hard enough for God to save them?
Think about it.