Candice,
I know some dc have more of a sensitivity towards content, and this is certainly something to ponder. You are such a loving mom, and while HOD weighs carefully the content for each age, only you know what will work for your dc and your family's needs. You've gotten some great advice and a lot to consider.
I can share my journey with this with you in the hopes that something here may help. I grew up in a church that only preached the love of God, which on the one hand was very nice, because I felt very loved!

On the other hand, it made me come to expect that nothing bad would happen, and it left me puzzled (and somewhat scared) when it did. For me, it would have been better to have a balance of what God's love is like, and what sin is like. I have found I'm thankful for the talks my dc and I have had about hardship in books we've read, especially in the Bible - and especially in books that do so in such a way to show how character and morals were displayed or developed through that hardship (i.e. heroes in history, martyrs in the Bible, etc.).
We have talks about how sin is a part of our fallen world we live in, and how these things make me very sad too. When our dc hear things on the radio, or hear people talking about difficult hardships to understand, we already have in place a basis for talking about these things. This has been such a good thing for us.
On the other hand, we avoid books that go into incessant gory details for the purpose of exalting the sin - an example of this for dc would be the Goosebumps series by R.L. Stine, or for adults, books by Stephen King. This kind of heavy/violent content is very different than the kind in the Bible. At Jesus' crucifixion, the Bible did NOT go into minute details about the torture of Jesus, how precisely he was hung on the cross in horrific detail, nor did it give play by play descriptions of His slow death and His many hours hanging on the cross. Entire books of the Bible could have dwelled on the many horrific details of His actual death, but instead less than a handful of pages describe it.
However, the Bible DOES give enough information for us to know just how difficult it was for Him to die for us - imagine how our appreciation for His sacrifice for us would change if the Bible only told us He was arrested, gave up His spirit and died, and now He is in heaven. Eliminating the heavy/violent details greatly diminishes understanding of the true sacrifice given.
The history books in HOD are chosen for this same balance - honesty in sharing hardships people have gone through so we can better appreciate what followed, and discretion in not sharing too much as if to celebrate the act of violence. So, only you will know what is too much for your dd's sensitive nature, but this thread has some great things to consider as you think through this. You are a wonderful mother to give this such thought - just be in prayer, and the Lord will help you make the best decisions!
In Christ,
Julie