She has a devastating background, but it doesn't justify her treatment of MC's family.

True, but she seemed like super angry and wanted to get revenge, and every time she woke up se was reminded of the fate she couldn't avoid. I think that makes your rage persevere against time... Until some certain day you understand how pointless it is. That's how I have perceived her feelings. It's a pity but that was something she could not avoid, and can only be healed with time.