Roman set Marla up to die
Before having his revenge for her cruel schemes against his mother, he decided that he might as well capitalise on her skills. After a year or so of her making them billions, he lured a grieving Feldstorm to Marla and had her killed when she felt most powerful. He presumably then attained full control of the company. Marla was abused by an elderly person when she was a child
Possibly assaulted by a stepfather or grandparent, which her mother either ignored or forced her to keep quiet on. This led Marla to gain a hatred of the elderly and disconnection with family, as well as a cynical and misanthropic attitude. Marla's mother disowned her due to her lesbianism
Marla's mother sexually abused her
Marla actually died during Roman's assassination attempt and the rest of the movie is just her dying thoughts
