How to get over accepting your partners step father abusing her for years

My previous partner who i am currently still very close with opened up to me about her step dad having hit her multiple times everyday and verbally anusing her. This has gone on for YEARS. 10 years. Her mother verbally insulting her too. She is no longer in that house thank god. It's just so horrible to hear how an innocent amazing person being treated with such disrespect because she wasn't wanted and her stepdad was never stopped. I ponder on it multiple times about her abuse and it makes me sad because it has caused a lot of psychological problems for her. She is amazing and love her to bits and you wouldn't even notice how much she's suffered on the surface. But it's so horrible she doesn't even want me complementing her... All because a collect of assholes in her life broke her self esteem.