TL;DR Angela’s mom was deluded into thinking that her spot beside the Marquis was stolen by Jayna’s mom and that everything Jayna and her mom has should’ve been for herself and Angela. Angela also shares this belief and is trying to “right the wrong”.
Angela’s white hair is a signature feature of ppl from the Holy Land. Angela’s mother is from the Holy Land and was sent to the empire as a “prize” for war heroes. During Angela’s mom’s stay in the capital, she fell in love the Marquis. However, the Marquis was in love with Jayna’s mom and they got married whereas Angela’s mom was set up by the emperor to wed Angela’s dad.
Angela’s dad is a commoner so he fought in the frontlines and developed PTSD. Due to his contributions to war, he was given a knight’s stipend and baron title, but the stipend was always given back to the people bc Angela’s dad has PTSD over killing ppl. So they lived an even poorer life than commoners. He also would beat up Angela’s mom and make her wear a pink dress (This is why Angela hates pink). Angela’s mom deludes herself and Angela into thinking that Jayna’s mom stole her rightful place by the Marquis’s side and that everything Jayna has should’ve been Angela’s.
At one point in Angela and Jayna’s childhood, Jayna and her mom visit Angela and her mom. And Angela actually plots a plan to kill Jayna and her mom by giving them poisonous cookies and Angela’s mom is all for it. Jayna doesn’t eat the cookies, but Jayna’s mom does and that how she dies.
Later on, when Angela’s dad accidentally kills Angela’s mom during a fit, he shifts his abuse to Angela and forced her to wear a pink dress (another reason why Angela hates pink). At one point, Angela kills her dad (by poison) and forges the adoption document to get into the Marquis’s palace.